Core body temperature (°C) of the infant taken on admission to the NICU or up to two hours after birth (Outcome 1.1)

Thirteen studies comprising 1633 infants reported core body temperature (°C rectal or axillary) on admission to the NICU (Chantaroj 2011; Farhadi 2012; Gathwala 2010; Knobel 2005; Reilly 2015; Rohana 2011; Smith 2013; Talakoub 2015; Trevisanuto 2010; Vohra 1999; Vohra 2004), at 30 minutes after birth (Cardona Torres 2012), and at one hour after birth (Leadford 2013). Reilly 2015 defined baseline temperature as temperature taken after cardiorespiratory stabilisation upon direct admission to the NICU or after arrival to the NICU if immediate resuscitation took place in the delivery room. Most studies reported that the time from birth to admission to the NICU ranged from around 20 minutes to 45 minutes; therefore, we included the 30‐minute temperature measurement from the Cardona Torres 2012 study, rather than the primary endpoint of 120 minutes. Each individual study showed a significant effect in favour of the intervention group (plastic wrap or bag) for infants across gestations, with the exception of Vohra 1999, which showed no significant differences in effect for the subgroup of infants at 28 to 31 weeks' gestation. Four studies did not provide subgroup data (Cardona Torres 2012; Chantaroj 2011; Gathwala 2010; Leadford 2013); we therefore grouped them together in the 'all infant' category with a range of gestations from 26 to 37 weeks. Although infants in the Knobel 2005 and Trevisanuto 2010 studies had gestation < 29 completed weeks and Smith 2013 ≤ 29 completed weeks, we included these infants in the < 28 completed weeks subgroup for meta‐analysis. Four studies provided data for the subgroup ≥ 28 completed weeks, with a range of gestation from 28 to 33 weeks (Farhadi 2012; Rohana 2011; Talakoub 2015; Vohra 1999). The intervention consisted of plastic bags in 10 studies (Cardona Torres 2012; Chantaroj 2011; Farhadi 2012; Gathwala 2010; Knobel 2005; Leadford 2013; Talakoub 2015; Trevisanuto 2010; Vohra 1999; Vohra 2004), and three studies provided plastic wrap (or a bag cut similar to wrap) as the intervention (Reilly 2015; Rohana 2011; Smith 2013).

Outcome 1.1.1: Overall for infants at < 37 weeks' gestation, data show a statistically significant difference in core body temperature on admission to the NICU favouring the intervention group (plastic wrap or bag) compared with those who received routine care immediately after birth in the delivery room (mean difference (MD) 0.58°C, 95% confidence interval (CI) 0.50 to 0.66; 13 studies; N = 1633) (Analysis 1.1). However, the overall test for homogeneity and for each subgroup of infants failed, with an I² value ranging from 59% to 61% (moderate heterogeneity).

Outcome 1.1.2: For infants at < 28 weeks' gestation, data show a statistically significant difference in core body temperature on admission to the NICU favouring the intervention group (plastic wrap or bag) when compared with those who received routine care immediately after birth in the delivery room (MD 0.65°C, 95% CI 0.52 to 0.79; eight studies; N = 1171) (Analysis 1.1). However, the test for homogeneity failed, with an I² value of 61% (moderate heterogeneity).

Outcome 1.1.3: For infants at ≥ 28 weeks' gestation, data show a statistically significant difference in core body temperature on admission to the NICU favouring the intervention group (plastic wrap or bag) when compared with those who received routine care immediately after birth in the delivery room (MD 0.56°C, 95% CI 0.34 to 0.78; four studies, n = 200) (Analysis 1.1). However, the test for homogeneity failed, with an I² value of 60% (moderate heterogeneity).

Publication bias and investigation of heterogeneity

Owing to the substantial heterogeneity observed, we inspected a funnel plot comparison for plastic wrap or bag versus routine care for core body temperature (°C) on admission to the NICU or up to two hours after birth for possible publication bias (Figure 3). When we removed Vohra 2004 from the meta‐analysis of all studies (< 37 weeks' gestation), data show no change in the effect measure (MD 0.58°C, 95% CI 0.50 to 0.66; 12 studies; N = 1580). Heterogeneity remained moderate at 61%. Publication bias was potentially problematic for the subgroup of studies presenting data for infants at < 28 weeks' gestation, suggesting that non‐effect, smaller studies have not been published. To overcome this, we removed from the meta‐analysis the following studies with 95% confidence limits > 1, with an I² value of 0%: Rohana 2011; Vohra 1999; and Vohra 2004 (MD 0.57°C, 95% CI 0.42 to 0.71; five studies; N = 1063). For the study subgroup presenting data for infants at ≥ 28 weeks' gestation, upon removal of Farhadi 2012 (MD 0.49°C, 95% CI 0.26 to 0.72; three studies; N = 178), heterogeneity remained moderate, with an I² value of 55%.

Figure 3

---

---

Funnel plot of comparison: 1 Plastic wrap or bag versus routine care, outcome: 1.1 Core body temperature (°C) on admission to NICU or up to 2 hours after birth.

Hypothermia on admission to the NICU (core body temperature < 36.5°C, or skin temperature < 36°C) (Outcome 1.2)

Ten studies comprising 1417 infants, in addition to reporting core body temperature on admission to the NICU as a continuous variable, provided data in a dichotomous format in terms of the incidence of hypothermia in intervention and control groups (plastic wrap or bag and routine care) (Cardona Torres 2012; Chantaroj 2011; Farhadi 2012; Knobel 2005; Leadford 2013; Reilly 2015; Rohana 2011; Trevisanuto 2010; Vohra 1999; Vohra 2004). Cardona Torres 2012 reported hypothermia throughout the study period of 120 minutes, and Leadford 2013 reported hypothermia one hour after birth. Most studies defined hypothermia as a core body temperature (rectal or axillary) < 36.5°C on admission to the NICU, and two studies defined hypothermia as a core body temperature (rectal or axillary) < 36.4°C on admission to the NICU (Knobel 2005; Trevisanuto 2010). Reilly 2015 reported hypothermia defined as core body temperature (axillary) < 36.5°C at baseline (after cardiorespiratory stabilisation upon direct admission to the NICU, or after arrival to the NICU if immediate resuscitation took place in the delivery room). Cardona Torres 2012 provided no clear definition. For Vohra 1999 and Vohra 2004, we derived data from a graph of core body temperatures on admission to the NICU versus birth weight for control and intervention groups; core body temperature (rectal) was defined as < 35.0°C, and no subgroup data were available.

Most individual studies showed a significant effect in favour of the intervention (plastic wrap or bag group), with the exception of Chantaroj 2011, which showed no differences in effect for infants at < 28 weeks' gestation; however the number of infants in this subgroup was very small. The small trials of Vohra 1999 and Cardona Torres 2012 showed borderline significant effects favouring the plastic wrap or bag group.

Outcome 1.2.1: Overall, for infants at < 37 weeks' gestation, plastic wrap or bag significantly reduced risk of hypothermia on admission to the NICU (typical RR 0.67, 95% CI 0.62 to 0.72; typical risk difference (RD) ‐0.25, 95% CI ‐0.29 to ‐0.20; 10 studies; N = 1417) (Analysis 1.2). Four infants would have to be wrapped in plastic to prevent one infant from becoming hypothermic (NNTB 4, 95% CI 4 to 5). The overall test for homogeneity failed, with an I² value of 65% (moderate heterogeneity) for RR and 70% (moderate heterogeneity) for RD, as well as for subgroup differences, with an I² value of 78.5% (high heterogeneity) for RR and 91.6% (high heterogeneity) for RD.

Outcome 1.2.2: For infants at < 28 weeks' gestation, plastic wrap or bag significantly reduced risk of hypothermia on admission to NICU (typical RR 0.70, 95% CI 0.65 to 0.77; typical RD ‐0.23, 95% CI ‐0.29 to ‐0.18; six studies; N = 1029) (Analysis 1.2).

This finding is consistent with those for outcome measure 1.1.2. Four infants would have to be wrapped in plastic to prevent one infant from becoming hypothermic (NNTB 4, 95% CI 4 to 6). The test for homogeneity passed with an I² value of 44% (low heterogeneity) for RR but with I² of 67% (moderate heterogeneity) for RD.

Outcome 1.2.3: For infants at ≥ 28 weeks' gestation, plastic wrap or bag significantly reduced risk of hypothermia on admission to the NICU (typical RR 0.17, 95% CI 0.07 to 0.43; typical RD ‐0.71, 95% CI ‐0.89 to ‐0.52; two studies; N = 55) (Analysis 1.2). This finding is consistent with those reported for outcome measure 1.1.3. One infant would have to be wrapped in plastic to prevent one infant from becoming hypothermic (NNTB 1 95% CI 1 to 2). The test for homogeneity passed with an I² value of 0% for both RR and RD.

Computational errors can occur when a zero count is seen in one or both arms of a study, as in Cardona Torres 2012 and Vohra 1999. RevMan software compensates by adding 0.5 to each cell.

Publication bias and investigation of heterogeneity

Owing to the substantial heterogeneity noted above, we inspected a funnel plot comparison (SE(log (RR)) vs RR) for plastic wrap or bag versus routine care for hypothermia on admission to the NICU for possible publication bias. Figure 4 shows that publication bias may be present, suggesting that non‐effect, smaller studies have not been published. Upon removal from the meta‐analysis of small studies showing a significant effect with SE(log (RR)) above 0.3 (Cardona Torres 2012; Chantaroj 2011; Farhadi 2012; Vohra 1999; Vohra 2004), the overall test for heterogeneity passed with an I² value of 0%, and the effect size remained highly significant (typical RR 0.72, 95% CI 0.67 to 0.78; five studies; N = 1167). For the subgroup of studies presenting data for infants at < 28 weeks' gestation, upon removal of two studies from the meta‐analysis (Farhadi 2012; Vohra 2004), the overall test for heterogeneity passed with I² of 0%, and the effect size remained highly significant (typical RR 0.73, 95% CI 0.67 to 0.79; four studies; N = 958).

Figure 4

---

---

Funnel plot of comparison: 1 Plastic wrap or bag versus routine care, outcome: 1.2 Hypothermia on admission to NICU: core body temperature < 36.5°C or skin temperature < 36°C.

Outside normothermic range on admission to the NICU or up to two hours after birth (Outcome 1.3)

Five studies comprising 1048 infants reported this outcome, or it was derived from definitions of hypothermia and hyperthermia as the incidence of a core body temperature outside the normothermic range on admission to the NICU (Chantaroj 2011; Farhadi 2012; Leadford 2013; Reilly 2015; Trevisanuto 2010). Chantaroj 2011 and Farhadi 2012 defined normothermia as core body temperature (rectal or axillary) of 36.5°C to 37.5°C, Reilly 2015 as core body temperature (axillary) of 36.5°C to 37.4°C (baseline), Trevisanuto 2010 as core body temperature (axillary) of 36.4°C to 37.5°C, and Leadford 2013 as core body temperature (axillary) of 36.5°C to 37.5°C at one hour after birth. Most individual studies showed a significant effect favouring the intervention (plastic wrap or bag group), with the exception of Chantaroj 2011, which showed no difference in effect for infants at < 28 weeks' gestation; however, the number of infants in this subgroup was very small. Trevisanuto 2010 showed a borderline significant effect favouring the plastic wrap or bag group. This was not a prespecified outcome at the review protocol stage.

Outcome 1.3.1: Overall, for infants at < 37 weeks' gestation, plastic wrap or bag significantly reduced the risk of a core body temperature outside the normothermic range on admission to the NICU (typical RR 0.75, 95% CI 0.69 to 0.81; typical RD ‐0.20, 95% CI ‐0.26 to ‐0.15; five studies; N = 1048) (Analysis 1.3). Five infants would have to be wrapped in plastic to prevent one infant from having a core body temperature outside the normothermic range (NNTB 5, 95% CI 4 to 7). The overall test for homogeneity failed, with an I² value of 77% (high heterogeneity) for RR and 87% (high heterogeneity) for RD, and also for subgroup differences with an I² value of 77% (high heterogeneity) for RR and 92.5% (high heterogeneity) for RD.

Outcome 1.3.2: For infants at < 28 weeks' gestation, plastic wrap or bag significantly reduced the risk of being outside the normothermic range on admission to the NICU (typical RR 0.81, 95% CI 0.75 to 0.88; typical RD ‐0.15, 95% CI ‐0.21 to ‐0.10; three studies; N = 871) (Analysis 1.3). Seven infants would have to be wrapped in plastic to prevent one infant from having a core body temperature outside the normothermic range on admission to the NICU (NNTB 7, 95% CI 5 to 10). The test for homogeneity passed, with an I² value of 0% for RR and I² of 38% (low heterogeneity) for RD.

Outcome 1.3.3: For infants at ≥ 28 weeks' gestation, plastic wrap or bag significantly reduced the risk of being outside the normothermic range on admission to the NICU (RR 0.14, 95% CI 0.04 to 0.52; RD ‐0.76, 95% CI ‐0.98 to ‐0.53; one study; N = 33) (Analysis 1.3). One infant would have to be wrapped in plastic to prevent one infant from having a core body temperature outside the normothermic range on admission to the NICU (NNTB 1, 95% CI 1 to 2).

Core body temperature one hour after birth (Outcome 1.4)

One study reported this outcome in terms of core body temperature in °C (axillary) every 15 minutes until two hours after birth (Cardona Torres 2012). This was not a prespecified outcome at the review protocol stage.

Outcome 1.4.1: For infants at ≥ 28 and < 37 weeks' gestation and birth weight ≥ 1000 and ≤ 2499 grams, a statistically significant difference in core body temperature one hour after birth favoured the intervention (plastic wrap or bag) group when compared with the group that received routine care immediately after birth in the delivery room (MD 0.40°C, 95% CI 0.19 to 0.61; one study; N = 60) (Analysis 1.4).

Core body temperature 90 minutes after birth (Outcome 1.5)

One study reported this outcome in terms of core body temperature in °C (axillary) every 15 minutes until two hours after birth (Cardona Torres 2012). This was not a prespecified outcome at the review protocol stage.

Outcome 1.5.1: For infants at ≥ 28 and < 37 weeks' gestation and birth weight ≥ 1000 and ≤ 2499 grams, a statistically significant difference in core body temperature 90 minutes after birth favoured the intervention (plastic wrap or bag) group when compared with the group that received routine care immediately after birth in the delivery room (MD 0.40°C, 95% CI 0.18 to 0.62; one study; N = 60) (Analysis 1.5).

Core body temperature two hours after birth (Outcome 1.6)

One study reported this outcome in terms of core body temperature in °C (axillary) every 15 minutes until two hours after birth (Cardona Torres 2012). This was not a prespecified outcome at the review protocol stage.

Outcome 1.6.1: For infants at ≥ 28 and < 37 weeks' gestation and birth weight ≥ 1000 and ≤ 2499 grams, a statistically significant difference in core body temperature two hours after birth favoured the intervention (plastic wrap or bag) group when compared with the group that received routine care immediately after birth in the delivery room (MD 0.30°C, 95% CI 0.13 to 0.47; one study; N = 60) (Analysis 1.6).

Core body temperature post stabilisation (Outcome 1.7)

Two studies comprising 911 infants reported this outcome in terms of core body temperature in °C (axillary) post stabilisation in the NICU (Reilly 2015; Rohana 2011). Reilly 2015 defined post stabilisation as temperature taken after admission procedures were completed and the infant was left to rest in a stable thermoneutral environment. Rohana 2011 defined post stabilisation as temperature taken once respiratory support, peripheral lines, and cardiorespiratory monitor probes had been secured. This was not a prespecified outcome at the review protocol stage. Each individual study showed a significant effect in favour of the intervention (plastic wrap or bag) group for infants at < 28 weeks' gestation; however Rohana 2011 showed no (borderline) significant difference in effect for the subgroup of infants at ≥ 28 weeks' gestation.

Outcome 1.7.1: Overall, for infants at ≥ 24 and ≤ 33 weeks' gestation, a statistically significant difference in core body temperature post stabilisation favoured the intervention (plastic wrap or bag) group when compared with the group that received routine care immediately after birth in the delivery room (MD 0.43°C, 95% CI 0.22 to 0.64; two studies; N = 911) (Analysis 1.7). The overall test for homogeneity passed with an I² value of 0%.

Outcome 1.7.2: For infants at < 28 weeks' gestation, a statistically significant difference in core body temperature post stabilisation favoured the intervention (plastic wrap or bag) group when compared with the group that received routine care immediately after birth in the delivery room (MD 0.44°C, 95% CI 0.20 to 0.67; two studies; N = 838) (Analysis 1.7). The test for homogeneity passed with an I² value of 0%.

Outcome 1.7.3: For infants at ≥ 28 weeks' gestation, a borderline statistically significant difference in core body temperature post stabilisation favoured the intervention (plastic wrap or bag) group when compared with the group that received routine care immediately after birth in the delivery room (MD 0.40°C, 95% CI ‐0.00 to 0.80; one study; N = 73) (Analysis 1.7).

Hypothermia post stabilisation: core body temperature < 36.5°C, or skin temperature < 36°C (Outcome 1.8)

Two studies comprising 841 infants reported this outcome in terms of incidence of hypothermia in intervention and control groups (plastic wrap or bag and routine care) (Farhadi 2012; Reilly 2015). Hypothermia post stabilisation was defined as core body temperature (axillary) < 36.5°C. Reilly 2015 defined 'post stabilisation' as temperature taken after admission procedures were completed and the infant was left to rest in a stable thermoneutral environment; we utilised incidence of hypothermia one hour after admission to the NICU for Farhadi 2012. This was not a prespecified outcome at the review protocol stage. Each individual study showed a significant effect in favour of the intervention (plastic wrap or bag) group across gestations.

Overall

For infants at ≤ 32 weeks' gestation, plastic wrap or bag significantly reduced the risk of hypothermia post stabilisation (typical RR 0.76, 95% CI 0.65 to 0.88; typical RD ‐0.13, 95% CI ‐0.19 to ‐0.06; two studies; N = 841) (Analysis 1.8). Eight infants would have to be wrapped in plastic to prevent one infant from being hypothermic post stabilisation (NNTB 8, 95% CI 5 to 17). The overall test for homogeneity failed with an I² value of 76% (high heterogeneity) for RR and I² of 91% (high heterogeneity) for RD, and for subgroup differences with I² values of 74.7% (moderate heterogeneity) for RR and 90.7% (high heterogeneity) for RD.

Outcome 1.8.1: For infants at ≤ 32 weeks' gestation (when no subgroup data were available), plastic wrap or bag significantly reduced the risk of hypothermia post stabilisation (RR 0.05, 95% CI 0.00 to 0.76; RD ‐0.50, 95% CI ‐0.72 to ‐0.28; one study; N = 40) (Analysis 1.8). Two infants would have to be wrapped in plastic to prevent one infant from being hypothermic post stabilisation (NNTB 2, 95% CI 1 to 4).

Outcome 1.8.2: For infants at ≥ 24 and < 28 weeks' gestation, plastic wrap or bag significantly reduced the risk of hypothermia post stabilisation (RR 0.79, 95% CI 0.69 to 0.92; RD ‐0.11, 95% CI ‐0.18 to ‐0.04; one study; N = 801) (Analysis 1.8). Nine infants would have to be wrapped in plastic to prevent one infant from being hypothermic post stabilisation (NNTB 9, 95% CI 6 to 25).

Outside the normothermic range post stabilisation (Outcome 1.9)

Two studies comprising 841 infants reported this outcome, or it was derived from definitions of hypothermia and hyperthermia in terms of incidence outside the normothermic range post stabilisation in intervention and control groups (plastic wrap or bag and routine care) (Reilly 2015), as well as one hour after admission to the NICU (Farhadi 2012). Reilly 2015 defined normothermia as core body temperature (rectal or axillary) of 36.5°C to 37.4°C, and Farhadi 2012 as core body temperature (axillary) of 36.5°C to 37.5°C. This was not a prespecified outcome at the review protocol stage. Farhadi 2012 showed a significant effect favouring the intervention (plastic wrap or bag) group for infants at ≤ 32 weeks' gestation (when no subgroup data were available), and Reilly 2015 showed no significant difference in effect for the subgroup of infants at < 28 weeks' gestation.

Overall

For infants at ≤ 32 weeks' gestation, data show no significant difference (borderline) in the risk of having a core body temperature outside the normothermic range post stabilisation (typical RR 0.88, 95% CI 0.78 to 1.00; typical RD ‐0.07, 95% CI ‐0.13 to 0.00; two studies; N = 841) (Analysis 1.9). The overall test for homogeneity failed with an I² value of 80% (high heterogeneity) for RR and I² of 90% (high heterogeneity) for RD, and with I² values of 79.6% (high heterogeneity) for RR and 90.1% (high heterogeneity) for RD for subgroup differences.

Outcome 1.9.1: For infants at ≤ 32 weeks' gestation (when no subgroup data were available), plastic wrap or bag significantly reduced the risk of having a core body temperature outside the normothermic range one hour after admission to the NICU (RR 0.10, 95% CI 0.01 to 0.71; RD ‐0.45, 95% CI ‐0.69 to ‐0.21; one study; N = 40) (Analysis 1.9). Two infants would have to be wrapped in plastic to prevent one infant from being outside the normothermic range (NNTB 2, 95% CI 2 to 5).

Outcome 1.9.2: For infants at ≥ 24 and < 28 weeks' gestation, data show no significant difference in the risk of having a core body temperature outside the normothermic range post stabilisation (RR 0.92, 95% CI 0.81 to 1.04; RD ‐0.05, 95% CI ‐0.12 to 0.02; one study; N = 801) (Analysis 1.9).

Core body temperature 30 minutes after the initial NICU admission temperature was taken (Outcome 1.10)

One study reported this outcome in terms of core body temperature in °C (axillary) 30 minutes after the initial NICU admission temperature was taken (Smith 2013). This was not a prespecified outcome at the review protocol stage.

Outcome 1.10.1: For infants at ≤ 29 weeks' gestation, data show a statistically significant difference in core body temperature 30 minutes after the initial NICU temperature was taken favouring the intervention (plastic wrap or bag) group over the group that received routine care immediately after birth in the delivery room (MD 0.57°C, 95% CI 0.27 to 0.87; one study; N = 92) (Analysis 1.10).

Core body temperature one hour after the initial NICU admission temperature was taken (Outcome 1.11)

Six studies comprising 373 infants reported this outcome in terms of core body temperature in °C (rectal or axillary) one hour after the initial NICU admission temperature was taken (Farhadi 2012; Gathwala 2010; Smith 2013; Talakoub 2015; Trevisanuto 2010; Vohra 2004). This was not a prespecified outcome at the review protocol stage. The purpose for collection of this outcome measure was to ascertain whether the intervention (plastic wrap or bag) prevented rather than delayed the postnatal fall in body temperature immediately after birth. Most individual studies showed an effect favouring the plastic wrap or bag, with the exception of Gathwala 2010 for infants at ≤ 32 weeks' gestation and birth weight ≤ 1500 grams, Talakoub 2015 for infants at 28 to 32 weeks' gestation, and Vohra 2004 for infants at < 28 weeks' gestation, which tended towards favouring the plastic wrap or bag group.

Outcome 1.11.1: Overall, for infants at < 37 weeks' gestation, a statistically significant difference shown for core body temperature one hour after the initial NICU admission temperature was taken favours the intervention (plastic wrap or bag) group when compared with the group that received routine care immediately after birth in the delivery room (MD 0.36°C, 95% CI 0.25 to 0.47; six studies; N = 373) (Analysis 1.11). The overall test for homogeneity failed with an I² value of 80% (high heterogeneity) and I² of 74.6% (moderate heterogeneity) for subgroup differences.

Outcome 1.11.2: For infants at < 28 weeks' gestation, a statistically significant difference shown for core body temperature one hour after the initial NICU admission temperature was taken favoured the intervention (plastic wrap or bag) group when compared with the group that received routine care immediately after birth in the delivery room (MD 0.49°C, 95% CI 0.33 to 0.66; four studies; N = 227) (Analysis 1.11). The test for homogeneity passed with an I² value of 24%.

Outcome 1.11.3: For infants at ≥ 28 weeks' gestation, a statistically significant difference shown for core body temperature one hour after the initial NICU admission temperature was taken favoured the intervention (plastic wrap or bag) group when compared with the group that received routine care immediately after birth in the delivery room (MD 0.72°C, 95% CI 0.48 to 0.96; two studies; N = 86) (Analysis 1.11). The test for homogeneity passed with an I² value of 36% (low heterogeneity).

Core body temperature 90 minutes after the initial NICU admission temperature was taken (Outcome 1.12)

One study reported this outcome in terms of core body temperature in °C (axillary) 90 minutes after the initial NICU admission temperature was taken (Smith 2013). This was not a prespecified outcome at the review protocol stage.

Outcome 1.12.1: For infants at ≤ 29 weeks' gestation, a statistically significant difference shown for core body temperature 90 minutes after the initial NICU admission temperature was taken favoured the intervention (plastic wrap or bag) group when compared with the group that received routine care immediately after birth in the delivery room (MD 0.56°C, 95% CI 0.27 to 0.85; one study; N = 92) (Analysis 1.12).

Core body temperature two hours after the initial NICU admission temperature was taken (Outcome 1.13)

Two studies comprising 156 infants reported this outcome in terms of core body temperature in °C (axillary) two hours after the initial NICU admission temperature was taken (Smith 2013; Talakoub 2015). This was not a prespecified outcome at the review protocol stage. Each individual study showed a significant effect in favour of the intervention (plastic wrap or bag) group for infants across gestations.

Overall

Overall, for infants at ≤ 32 weeks' gestation, a statistically significant difference shown for core body temperature two hours after the initial NICU admission temperature was taken favoured the intervention (plastic wrap or bag) group when compared with the group that received routine care immediately after birth in the delivery room (MD 0.37°C, 95% CI 0.16 to 0.59; two studies; N = 156) (Analysis 1.13). The test for homogeneity failed with an I² value of 64% (moderate heterogeneity).

Outcome 1.13.1: For infants at ≤ 29 weeks' gestation, a statistically significant difference was shown for core body temperature two hours after the initial NICU admission temperature was taken favouring the intervention (plastic wrap or bag) group when compared with the group that received routine care immediately after birth in the delivery room (MD 0.28°C, 95% CI 0.04 to 0.52; one study; N = 92) (Analysis 1.13).

Outcome 1.13.2: For infants at 28 to 32 weeks' gestation, a statistically significant difference was shown for core body temperature two hours after the initial NICU admission temperature was taken favouring the intervention (plastic wrap or bag) group when compared with the group that received routine care immediately after birth in the delivery room (MD 0.74°C, 95% CI 0.26 to 1.22; one study; N = 64) (Analysis 1.13).

Hyperthermia on admission to the NICU: core body temperature > 37.5°C (Outcome 1.14)

Twelve studies comprising 1523 infants reported this outcome in terms of incidence of hyperthermia in the intervention and control groups (plastic wrap or bag and routine care). Some investigators defined hyperthermia as core body temperature (rectal or axillary) > 37.5°C (Chantaroj 2011; Farhadi 2012; Smith 2013; Trevisanuto 2010; Vohra 2004), Reilly 2015 as core body temperature (axillary) ≥ 37.5°C, and Leadford 2013 as core body temperature (axillary) > 38°C; five studies did not provide a clear definition (Cardona Torres 2012; Gathwala 2010; Knobel 2005; Talakoub 2015; Vohra 1999). This was not the prespecified definition at the review protocol stage. For the purposes of this meta‐analysis, review authors interpreted 'no risk of hyperthermia' as reported in Talakoub 2015 as no hyperthermia in intervention or control groups (trial authors have been contacted).

Each individual study showed no significant difference in risk of hyperthermia across gestations, with the exception of a large multi‐centre study, which showed that plastic wrap significantly increased the risk of being hyperthermic on admission to the NICU for infants at < 28 weeks' gestation (Reilly 2015).

Outcome 1.14.1: Overall, for infants at < 37 weeks' gestation, plastic wrap or bag significantly increased the risk of being hyperthermic on admission to the NICU (typical RR 3.91, 95% CI 2.05 to 7.44; typical RD 0.04, 95% CI 0.02 to 0.06; twelve studies; N = 1523) (Analysis 1.14). Twenty‐five infants would have to be wrapped in plastic to have one infant hyperthermic on admission to the NICU (NNTH 25, 95% CI 17 to 50). The overall test for homogeneity passed with an I² value of 0% for RR and 19% for RD. For subgroup differences, homogeneity passed with an I² value of 0% for RR and 47.7% (low heterogeneity) for RD.

Note: RR was not estimable for five studies owing to zero events in both arms.

Outcome 1.14.2: For infants at < 28 weeks' gestation, plastic wrap or bag significantly increased the risk of being hyperthermic on admission to the NICU (typical RR 4.00, 95% CI 2.04 to 7.83; typical RD 0.05, 95% CI 0.03 to 0.08; seven studies; N = 1121) (Analysis 1.14). Twenty infants would have to be wrapped in plastic to have one infant hyperthermic on admission to the NICU (NNTH 20, 95% CI 13 to 33). The overall test for homogeneity passed with an I² value of 14% for RR and 0% for RD.

Outcome 1.14.3: For infants at ≥ 28 weeks' gestation, data show no statistically significant differences between the two interventions (plastic bag and routine care) for being hyperthermic on admission to the NICU (typical RR (not estimable); typical RD 0.00, 95% CI ‐0.05 to 0.05; three studies; N = 138) (Analysis 1.14). The overall test for homogeneity passed with an I² value of 0% for RD.

In addition, Rohana 2011 reported that two infants in the wrap group were hyperthermic (> 37.5°C) within the first 12 hours of life (for infants at ≥ 24 and ≤ 33 weeks' gestation).

Publication bias and investigation of heterogeneity

Data show no evidence of publication bias.

Hyperthermia post stabilisation: core body temperature > 37.5°C (Outcome 1.15)

One study reported this outcome in terms of incidence of hyperthermia in intervention and control groups (plastic wrap or bag and routine care) post stabilisation (Reilly 2015). Investigators defined hyperthermia as core body temperature (axillary) ≥ 37.5°C. Reilly 2015 defined post stabilisation as temperature taken after admission procedures were completed and the infant was left to rest in a stable thermoneutral environment. This was not our prespecified definition at the review protocol stage.

Outcome 1.15.1: For infants at ≥ 24 and < 28 weeks' gestation, plastic wrap or bag significantly increased risk of being hyperthermic post stabilisation (RR 2.35, 95% CI 1.38 to 4.00; RD 0.06, 95% CI 0.02 to 0.10; one study; N = 801) (Analysis 1.15). Seventeen infants would have to be wrapped in plastic to have one infant hyperthermic post stabilisation (NNTH 17, 95% CI 10 to 50).

Major brain injury

Major brain injury (defined as sonographic evidence of intraventricular haemorrhage (IVH) with ventricular dilatation, parenchymal haemorrhagic infarction, or periventricular leukomalacia) (Outcome 1.16)

One review author (HH) reviewed data definitions for brain injury (all grades) across all studies and allocated individual outcomes to an appropriate composite outcome for the purposes of meta‐analysis. This composite outcome was not prespecified at the review protocol stage. Five studies comprising 1100 infants reported this outcome (Knobel 2005; Reilly 2015; Rohana 2011; Smith 2013; Trevisanuto 2010). Knobel 2005 and Trevisanuto 2010 defined major brain injury as sonographic evidence of IVH with ventricular dilatation, parenchymal haemorrhagic infarction, or periventricular leukomalacia. Rohana 2011 provided data for severe IVH grade Ⅲ and Ⅳ. Reilly 2015 provided data separately for severe IVH grade Ⅲ and Ⅳ and for cystic periventricular leukomalacia. These were not mutually exclusive; therefore we used cystic periventricular leukomalacia in this meta‐analysis. Smith 2013 provided data for cystic periventricular leukomalacia. Each individual study showed no significant differences in effect across gestations.

Overall

For infants at ≤ 33 weeks' gestation, data show no significant difference in risk of major brain injury between infants who received plastic wrap or bag and those given routine care (typical RR 0.78, 95% CI 0.47 to 1.27; typical RD ‐0.01, 95% CI ‐0.04 to 0.01; five studies; N = 1100) (Analysis 1.16). The overall test for homogeneity passed with an I² value of 0% for both RR and RD and for subgroup differences.

Outcome 1.16.1: For infants at ≤ 33 weeks' gestation (when no subgroup data were available), data show no significant difference in risk of major brain injury between infants who received plastic wrap or bag and those given routine care (RR 0.30, 95% CI 0.03 to 2.60; RD ‐0.05, 95% CI ‐0.12 to 0.03; one study; N = 110) (Analysis 1.16).

Outcome 1.16.2: For infants at < 28 weeks' gestation, data show no significant difference in risk of major brain injury between infants who received plastic wrap or bag and those given routine care (typical RR 0.83, 95% CI 0.50 to 1.39; typical RD ‐0.01, 95% CI ‐0.04 to 0.02; four studies; n = 990) (Analysis 1.16). The test for homogeneity passed with an I² value of 0% for both RR and RD.

Brain injury (Outcome 1.17)

Three studies comprising 880 infants reported this outcome in terms of incidence of all grades of IVH (Ⅰ to Ⅳ) in intervention and control groups (plastic wrap or bag and routine care) (Farhadi 2012; Reilly 2015; Smith 2013). Each individual study showed no significant difference in effect for infants at < 28 weeks' gestation.

Outcome 1.17.1: For infants at < 28 weeks' gestation, data show no significant difference in risk of any grade IVH between infants who received plastic wrap or bag and those given routine care (typical RR 0.92, 95% CI 0.77 to 1.09; typical RD ‐0.03, 95% CI ‐0.09 to 0.03; three studies; N = 880) (Analysis 1.16). The test for homogeneity passed with an I² value of 0% for both RR and RD.

Intraventricular haemorrhage grades Ⅲ and Ⅳ (Outcome 1.18)

One study (for which data have not been meta‐analysed in outcome 1.16) reported this outcome in terms of incidence of severe IVH (grades Ⅲ and Ⅳ) in intervention and control groups (plastic wrap and routine care) (Reilly 2015).

Outcome 1.18.1: For infants at ≥ 24 and < 28 weeks' gestation, data show no significant difference in risk of major brain injury between infants who received plastic wrap and those given routine care (RR 0.99, 95% CI 0.67 to 1.46; RD ‐0.00, 95% CI ‐0.05 to 0.05; one study; N = 753) (Analysis 1.18).

Mortality (death before hospital discharge or at six months' corrected age) (Outcome 1.19)

Ten studies comprising 1447 infants reported this outcome in terms of incidence of death within hospital stay or at six months' corrected age if infants in hospital in intervention and control groups (plastic wrap or bag and routine care) remain in hospital (Chantaroj 2011; Farhadi 2012; Knobel 2005; Leadford 2013; Reilly 2015; Rohana 2011; Smith 2013; Trevisanuto 2010; Vohra 1999; Vohra 2004). Mortality figures for Vohra 2004 included two infants who died in the delivery room. The study with greatest weighting (64.6%) in the meta‐analysis was powered for all‐cause mortality (at discharge or at six months' corrected gestation, if the infant remains in hospital) as the primary outcome measure (Reilly 2015). Mortality was a secondary outcome measure in the remaining nine studies. Each individual study showed no significant difference in effect across gestations.

Outcome 1.19.1: Overall, for infants at < 37 weeks' gestation, results of the meta‐analysis generally favour the intervention group (plastic wrap or bag), with the exception of Leadford 2013. However, overall data show no significant differences in risk of death within hospital stay (or at six months' corrected age) between infants who received plastic wrap or bag and those given routine care (typical RR 0.91, 95% CI 0.73 to 1.15; typical RD ‐0.01, 95% CI ‐0.05 to 0.02; 10 studies; N = 1447) (Analysis 1.19). The overall test for homogeneity passed with an I² value of 0% for RR and 22% for RD and for subgroup differences an I² value of 0%.

Outcome 1.19.2: For infants at < 28 weeks' gestation, data show no significant difference in risk of death within hospital stay (or at six months' corrected age) between infants who received plastic wrap or bag and those given routine care (typical RR 0.92, 95% CI 0.72 to 1.18; typical RD ‐0.02, 95% CI ‐0.06 to 0.03; six studies; N = 1114) (Analysis 1.19). The test for homogeneity passed with an I² value of 0% for RR but an I² value of 56% (moderate heterogeneity) for RD.

Outcome 1.19.3: For infants at 28 to 31 weeks' gestation, data show no significant difference in risk of death within hospital stay (or at six months' corrected age) between infants who received plastic wrap or bag and those given routine care (RR not estimable; RD 0.00, 95% CI ‐0.09 to 0.09; one study; N = 41) (Analysis 1.19).

Publication bias and investigation of heterogeneity

We inspected a funnel plot comparison (SE(log (RR)) vs RR) of mortality for plastic wrap or bag versus routine care for core body temperature in °C for possible publication bias (Figure 5). Findings suggest possible publication bias, but it is unlikely that this would affect findings of the meta‐analysis. On removal of two studies (Smith 2013; Vohra 1999), the test for homogeneity passed with an overall I² value of 0% (typical RR 0.98, 95% CI 0.77 to 1.24; eight studies; N = 1298), as did the test for the subgroup differences at < 28 weeks' gestation (typical RR 1.0, 95% CI 0.77 to 1.28; four studies; N = 1006).

Figure 5

---

---

Funnel plot of comparison: 1 Plastic wrap or bag versus routine care, outcome: 1.19 Mortality (death within hospital stay or at 6 months' corrected gestation).

Arterial oxygen saturation (percentage) (Outcome 1.20)

One study reported this outcome in terms of percentage oxygen saturation on admission to the NICU (Farhadi 2012). This was not a prespecified outcome at the review protocol stage.

Outcome 1.20.1: For infants at ≤ 32 weeks' gestation, data show no statistically significant differences between the two interventions (plastic bag and routine care) for arterial oxygen saturation (MD ‐4.10%, 95% CI ‐16.00 to 7.80; one study; N = 40) (Analysis 1.20).

Bicarbonate (mmol/L) (Outcome 1.21)

Two studies comprising 117 infants reported this outcome in terms of bicarbonate (mmol/L) (Trevisanuto 2010; Vohra 2004). This was not a prespecified outcome at the review protocol stage. Each individual study showed no significant differences in effect for infants at < 28 weeks' gestation.

Outcome 1.21.1: For infants at < 28 weeks' gestation, data show no statistically significant differences between the two interventions (plastic bag and routine care) for bicarbonate (MD 0.31 mmol/L, 95% CI ‐0.72 to 1.35; two studies; N = 117) (Analysis 1.21). The test for homogeneity passed with an I² value of 0%.

First blood gas pH (Outcome 1.22)

Two studies comprising 117 infants reported this outcome in terms of first blood gas pH (Trevisanuto 2010; Vohra 2004). This was not a prespecified outcome at the review protocol stage. Each individual study showed no significant differences in effect for infants at < 28 weeks' gestation. However, Vohra 2004 is tending towards favouring routine care, and Trevisanuto 2010 is tending towards favouring plastic bag.

Outcome 1.22.1: For infants at < 28 weeks' gestation, data show no statistically significant differences between the two interventions (plastic bag and routine care) for first blood gas pH (MD 0.01, 95% CI ‐0.02 to 0.04; two studies; N = 117) (Analysis 1.22). The test for homogeneity failed with an I² value of 70% (moderate heterogeneity). Because pH is on a logarithmic scale, it would be more appropriate to measure this outcome as a median value and range or interquartile range (IQR) to avoid its use as a continuous variable such as that prespecified at the review protocol stage: severe metabolic acidosis defined as pH < 7.20 and/or base deficit > 10 mmol/L within the first three days of life.

First blood gas pH < 7.25 (Outcome 1.23)

One study reported this outcome in terms of incidence of a first blood gas pH < 7.25 in intervention and control groups (plastic wrap and routine care) (Smith 2013).

Outcome 1.23.1: For infants at ≤ 29 weeks' gestation, data show no significant differences in risk of first blood gas pH < 7.25 between infants who received plastic wrap or bag and those given routine care (RR 0.81, 95% CI 0.55 to 1.20; RD ‐0.11, 95% CI ‐0.33 to 0.10; one study; N = 84) (Analysis 1.23).

First blood glucose concentration (mmol/L) (Outcome 1.24)

Four studies comprising 195 infants reported this outcome in terms of first blood glucose concentration (mmol/L) (Chantaroj 2011; Farhadi 2012; Trevisanuto 2010; Vohra 2004). When data were presented as mg/dL (USA Standard), we converted these to mmol/L (UK Standard). This was not a prespecified outcome at the review protocol stage, although hypoglycaemia defined by a blood glucose level < 2 mmol/L within two hours of birth was prespecified at the review protocol stage. Each individual study showed no significant differences in effect across gestations. Trevisanuto 2010 tended towards favouring plastic bag for infants at < 28 weeks' gestation.

Overall

For infants at ≤ 32 weeks' gestation, data show no statistically significant differences between the two interventions (plastic bag and routine care) for first blood glucose concentration (MD ‐0.14 mmol/L, 95% CI ‐0.50 to 0.21; four studies; N = 195). Overall, the test for homogeneity passed with an I² value of 11% but failed for subgroup differences with an I² value of 51.4% (moderate heterogeneity).

Outcome 1.24.1: For infants at ≤ 32 weeks' gestation (for whom no subgroup data were available), data show no statistically significant differences between the two interventions (plastic bag and routine care) for first blood glucose concentration (MD ‐0.62 mmol/L, 95% CI ‐1.37 to 0.12; two studies; N = 78) (Analysis 1.24). The test for homogeneity passed with an I² value of 0%.

Outcome 1.24.2: For infants at < 28 weeks' gestation, data show no statistically significant differences between the two interventions (plastic bag and routine care) for first blood glucose concentration (MD ‐0.00 mmol/L, 95% CI ‐0.41 to 0.41; two studies; N = 117) (Analysis 1.24). The test for homogeneity passed with an I² value of 0%.

First blood glucose concentration < 2.6 mmol/L (Outcome 1.25)

One study reported this outcome in terms of incidence of a first blood glucose concentration < 2.6 mmol/L in intervention and control groups (plastic wrap and routine care) (Smith 2013). This was not a prespecified outcome at the review protocol stage.

Outcome 1.25.1: For infants at ≤ 29 weeks' gestation, data show no significant difference in risk of first blood glucose concentration < 2.6 mmol/L between infants who received plastic wrap and those given routine care (RR 0.66, 95% CI 0.31 to 1.43; RD ‐0.10, 95% CI ‐0.28 to 0.08; one study; N = 85) (Analysis 1.25).

First blood glucose concentration > 6.0 mmol/L (Outcome 1.26)

One study reported this outcome of blood glucose concentration > 6.0 mmol/L in intervention and control groups (plastic wrap and routine care) (Smith 2013). This was not a prespecified outcome at the review protocol stage.

Outcome 1.26.1: For infants at ≤ 29 weeks' gestation, data show no significant difference in risk of first blood glucose concentration > 6.0 mmol/L between infants who received plastic wrap and those given routine care (RR 1.07, 95% CI 0.23 to 5.02; RD 0.00, 95% CI ‐0.10 to 0.11; one study; N = 85) (Analysis 1.26).

Blood glucose concentration (mmol/L) 120 minutes after birth (Outcome 1.27)

One study reported this outcome as a median value and IQR (Cardona Torres 2012). This was not a prespecified outcome at the review protocol stage.

Outcome 1.27.1: For infants at < 37 weeks' gestation, median blood glucose concentration (mmol/L) at 120 minutes after birth was comparable in intervention (plastic wrap or bag) and control (routine care) groups (one study; N = 60; P > 0.05) (Analysis 1.27).

Bronchopulmonary dysplasia (BPD) (Outcome 1.28)

One study reported this outcome in terms of a collapsed category analysis (Reilly 2015). Investigators provided no clear definition. This was not a prespecified outcome at the review protocol stage.

Outcome 1.28.1: For infants at ≥ 24 and < 28 weeks' gestation, data show no significant difference in risk of BPD between infants who received plastic wrap or bag and those given routine care (RR 0.99, 95% CI 0.86 to 1.15; RD ‐0.00, 95% CI ‐0.08 to 0.07; one study; N = 702) (Analysis 1.28).

Bronchopulmonary dysplasia (BPD) steroids (outcome 1.29)

One study reported this outcome in terms of incidence of BPD steroids in intervention and control groups (plastic wrap or bag and routine care) (Reilly 2015). This was not a prespecified outcome at the review protocol stage.

Outcome 1.29.1: For infants at ≥ 24 and < 28 weeks' gestation, data show no significant difference in risk of BPD steroids between infants who received plastic wrap or bag and those given routine care (RR 0.94, 95% CI 0.71 to 1.25; RD ‐0.01, 95% CI ‐0.07 to 0.04; one study; N = 796) (Analysis 1.29).

Duration of hospitalisation (days) (Outcome 1.30)

Two studies comprising 88 infants reported this outcome in terms of duration of hospital stay in days (Chantaroj 2011; Knobel 2005). Each individual study showed no significant difference in effect across gestations.

Overall

For infants at ≤ 32 weeks' gestation, data show no statistically significant differences between the two interventions (plastic bag and routine care) for duration of hospitalisation (MD ‐6.35 days, 95% CI ‐17.27 to 4.56; two studies; N = 126) (Analysis 1.30). Overall, the test for homogeneity passed with an I² value of 0% overall and for subgroup differences.

Outcome 1.30.1: For infants at ≤ 32 weeks' gestation or birth weight < 1500 grams (when no subgroup data were available), data show no statistically significant differences between the two interventions (plastic bag and routine care) for duration of hospitalisation (MD ‐7.50 days, 95% CI ‐24.17 to 9.17; one study; N = 38) (Analysis 1.30).

Outcome 1.30.2: For infants at < 28 weeks' gestation, data show no statistically significant differences between the two interventions (plastic bag and routine care) for duration of hospitalisation (MD ‐5.49 days, 95% CI ‐19.93 to 8.95; one study; N = 88) (Analysis 1.30).

Duration of hospitalisation (days) (Outcome 1.31)

One study reported this outcome as a median value with IQR (Rohana 2011).

Outcome 1.31.1: For infants at 24 to 33 weeks' gestation, median duration of hospitalisation was comparable in the intervention (plastic wrap) and control groups (routine care) (one study; N = 110; P = 0.29) (Analysis 1.31).

Duration of continuous positive airway pressure (CPAP) (days) (Outcome 1.32)

One study reported this outcome as a median value with IQR (Rohana 2011). This was not a prespecified outcome at the review protocol stage.

Outcome 1.32.1: For infants at 24 to 33 weeks' gestation, median duration (days) of CPAP was comparable in the intervention (plastic wrap) and control (routine care) groups (one study; N = 110; P = 0.29) (Analysis 1.32).

Duration of oxygen therapy (days) (Outcome 1.33)

One study reported this outcome in terms of duration of oxygen therapy (days) (Knobel 2005). This was not a prespecified outcome at the review protocol stage.

Outcome 1.33.1: For infants at < 29 weeks' gestation, data show no statistically significant differences between the two interventions (plastic bag and routine care) for duration of oxygen therapy (MD ‐6.51 days, 95% CI ‐23.30 to 10.28; one study; N = 88) (Analysis 1.33).

Duration of ventilation (days) (Outcome 1.34)

One study reported this outcome as a median value with IQR (Rohana 2011).

Outcome 1.34.1: For infants at 24 to 33 weeks' gestation, median duration of ventilation (days) was comparable in the intervention (plastic wrap) and control (routine care) groups (one study; N = 110; P = 0.30) (Analysis 1.34).

Gastrointestinal perforation (Outcome 1.35)

One study reported this outcome in terms of incidence of gastrointestinal perforation in the intervention and control groups (plastic wrap and routine care) (Reilly 2015). This was not a prespecified outcome at the review protocol stage.

Outcome 1.35.1: For infants at ≥ 24 and < 28 weeks' gestation, data show no significant differences in risk of gastrointestinal perforation between infants who received plastic wrap and those given routine care (RR 1.25, 95% CI 0.68 to 2.28; RD 0.01, 95% CI ‐0.02 to 0.04; one study; N = 795) (Analysis 1.35).

Intubation in delivery room (Outcome 1.36)

One study reported this outcome in terms of incidence of intubation in the delivery room in intervention and control groups (plastic bag and routine care) (Trevisanuto 2010).

Outcome 1.36.1: For infants at < 29 weeks' gestation, data show no significant differences in risk of intubation in the delivery room between infants who received plastic bag and those given routine care (RR 1.00, 95% CI 0.63 to 1.58; RD 0.00, 95% CI ‐0.24 to 0.24; one study; N = 64) (Analysis 1.36).

Necrotising enterocolitis (NEC) (Outcome 1.37)

Two studies comprising 907 infants reported this outcome in terms of incidence of NEC In intervention and control groups (plastic wrap and routine care) (Reilly 2015; Rohana 2011). Each individual study showed no significant difference in effect across gestations.

Overall for infants at ≥ 24 and ≤ 33 weeks' gestation, data show no significant differences in risk of NEC between infants who received plastic wrap and those given routine care (typical RR 1.01, 95% CI 0.65 to 1.58; typical RD 0.00, 95% CI ‐0.03 to 0.04; two studies; N = 907) (Analysis 1.37). Overall, the test for homogeneity passed with an I² value of 29% (low heterogeneity) for RR and 35% (low heterogeneity) for RD, and for subgroup differences an I² value of 28.6% (low heterogeneity) for RR and 26.9% (low heterogeneity) for RD.

Outcome 1.37.1: For infants at ≥ 24 and ≤ 33 weeks' gestation (when no subgroup data were available), data show no significant differences in risk of NEC between infants who received plastic wrap and those given routine care (RR 5.98, 95% CI 0.29 to 121.75; RD 0.04, 95% CI ‐0.02 to 0.10; one study; N = 110) (Analysis 1.37).

Outcome 1.37.2: For infants at ≥ 24 and < 28 weeks' gestation, data show no significant differences in risk of NEC between infants who received plastic wrap and those given routine care (RR 0.95, 95% CI 0.60 to 1.49; RD 0.00, 95% CI ‐0.04 to 0.03; one study; N = 797) (Analysis 1.37).

Patent ductus arteriosus (PDA) (Outcome 1.38)

Two studies comprising 905 infants reported this outcome in terms of incidence of PDA in intervention and control groups (plastic wrap and routine care) (Reilly 2015; Rohana 2011). Each individual study showed no significant differences in effect across gestations.

Overall for infants at ≥ 24 and ≤ 33 weeks' gestation, data show no significant differences in risk for PDA between infants who received plastic wrap and those given routine care (typical RR 0.90, 95% CI 0.78 to 1.03; typical RD ‐0.05, 95% CI ‐0.12 to 0.01; two studies; N = 905) (Analysis 1.38). Overall, the test for homogeneity passed with an I² value of 0% for RR and for RD, and for subgroup differences.

Outcome 1.38.1: For infants at ≥ 24 and ≤ 33 weeks' gestation (when no subgroup data were available), data show no significant differences in risk of PDA between infants who received plastic wrap and those given routine care (RR 0.80, 95% CI 0.39 to 1.62; RD ‐0.05, 95% CI ‐0.21 to 0.11; one study; N = 110) (Analysis 1.38).

Outcome 1.38.2: For infants at ≥ 24 and < 28 weeks' gestation, data show no significant differences in risk of PDA between infants who received plastic wrap and those given routine care (RR 0.90, 95% CI 0.79 to 1.04; RD ‐0.05, 95% CI ‐0.12 to 0.02; one study; N = 795) (Analysis 1.38).

Pneumothorax (Outcome 1.39)

One study reported this outcome in terms of incidence of pneumothorax in the intervention and control groups (plastic wrap and routine care) (Reilly 2015). This was not a prespecified outcome at the review protocol stage.

Outcome 1.39.1: For infants at ≥ 24 and < 28 weeks' gestation, data show no significant differences in risk of pneumothorax between infants who received plastic wrap and those given routine care (RR 0.98, 95% CI 0.56 to 1.69; RD ‐0.00, 95% CI ‐0.03 to 0.03; one study; N = 796) (Analysis 1.39).

Pulmonary haemorrhage (Outcome 1.40)

One study reported this outcome in terms of incidence of pulmonary haemorrhage during hospital stay in intervention and control groups (plastic wrap and routine care) (Reilly 2015). This was not a prespecified outcome at the review protocol stage.

Outcome 1.40.1: For infants at ≥ 24 and < 28 weeks' gestation, plastic wrap significantly reduced risk of pulmonary haemorrhage during hospital stay (RR 0.60, 95% CI 0.38 to 0.95; RD ‐0.04, 95% CI ‐0.08 to ‐0.01; one study; N = 796) (Analysis 1.40). Twenty‐five infants would have to be wrapped in plastic to prevent one infant from having a pulmonary haemorrhage (NNTB 25, 95% CI 13 to 100).

Requirement for bubble continuous positive airway pressure (BCPAP) (Outcome 1.41)

One study reported this outcome in terms of incidence of requirement for BCPAP in the intervention and control groups (plastic wrap and routine care) (Smith 2013). This was not a prespecified outcome at the review protocol stage.

Outcome 1.41.1: For infants at ≤ 29 weeks' gestation, data show no significant difference in risk of requirement for BCPAP between infants who received plastic wrap and those given routine care (RR 0.97, 95% CI 0.81 to 1.18; RD ‐0.02, 95% CI ‐0.18 to 0.13; one study; N = 92) (Analysis 1.41).

Requirement for ventilation (Outcome 1.42)

One study reported this outcome in terms of incidence of requirement for ventilation in intervention and control groups (plastic wrap and routine care) (Smith 2013).

Outcome 1.42.1: For infants at ≤ 29 weeks' gestation, data show no significant differences in risk of requirement for ventilation between infants who received plastic wrap and those given routine care (RR 0.92, 95% CI 0.70 to 1.20; RD ‐0.06, 95% CI ‐0.25 to 0.13; one study; N = 92) (Analysis 1.42).

Respiratory distress syndrome (RDS) (Outcome 1.43)

Two studies comprising 910 infants reported this outcome in terms of incidence of RDS in intervention and control groups (plastic wrap and routine care) (Reilly 2015; Rohana 2011). Each individual study showed no significant differences in effect across gestations.

Overall for infants at ≥ 24 and ≤ 33 weeks' gestation, data show no significant differences in risk of RDS between infants who received plastic wrap and those given routine care (typical RR 1.01, 95% CI 0.97 to 1.06; typical RD 0.01, 95% CI ‐0.03 to 0.05; two studies; N = 910) (Analysis 1.43). Overall, the test for homogeneity passed with an I² value of 0% overall for RR and RD, and for subgroup differences.

Outcome 1.43.1: For infants at ≥ 24 and ≤ 33 weeks' gestation (when no subgroup data were available), data show no significant differences in risk of RDS between infants who received plastic wrap and those given routine care (RR 1.04, 95% CI 0.78 to 1.38; RD 0.02, 95% CI ‐0.16 to 0.20; one study; N = 110) (Analysis 1.43).

Outcome 1.43.2: For infants at ≥ 24 and < 28 weeks' gestation, data show no significant differences in risk of RDS between infants who received plastic wrap and those given routine care (RR 1.01, 95% CI 0.97 to 1.05; RD 0.01, 95% CI ‐0.03 to 0.04; one study; N = 800) (Analysis 1.43).

Retinopathy of prematurity (ROP) (Outcome 1.44)

One study reported this outcome in terms of incidence of ROP in intervention and control groups (plastic wrap and routine care) (Reilly 2015). This was not a prespecified outcome at the review protocol stage.

Outcome 1.44.1: For infants at ≥ 24 and < 28 weeks' gestation, data show no significant differences in risk of gastrointestinal perforation between infants who received plastic wrap and those given routine care (RR 1.00, 95% CI 0.72 to 1.40; RD 0.00, 95% CI ‐0.06 to 0.06; one study; N = 606) (Analysis 1.44).

Sepsis (late) (Outcome 1.45)

Two studies comprising 830 infants reported this outcome in terms of incidence of late sepsis in intervention and control groups (plastic wrap and routine care) (Reilly 2015; Smith 2013). This was not a prespecified outcome at the review protocol stage. Each individual study showed no significant differences in effect for infants at ≤ 29 weeks' gestation.

Outcome 1.45.1: For infants at ≤ 29 weeks' gestation, data show no significant differences in risk of late sepsis between infants who received plastic wrap and those given routine care (typical RR 0.88, 95% CI 0.70 to 1.10; typical RD ‐0.03, 95% CI ‐0.09 to 0.02; two studies; N = 830) (Analysis 1.45). The test for homogeneity passed with an I² value of 9% for RR and 0% for RD.

Sepsis (early) (Outcome 1.46)

Two studies comprising 883 infants reported this outcome in terms of incidence of early sepsis in intervention and control groups (plastic wrap and routine care) (Reilly 2015; Smith 2013). This was not a prespecified outcome at the review protocol stage. Each individual study showed no significant differences in effect for infants at ≤ 29 weeks' gestation.

Outcome 1.46.1: For infants at ≤ 29 weeks' gestation, data show no significant differences in risk of early sepsis between infants who received plastic wrap and those given routine care (typical RR 0.69, 95% CI 0.38 to 1.29; typical RD ‐0.02, 95% CI ‐0.04 to 0.01; two studies; N = 883) (Analysis 1.46). The test for homogeneity passed with an I² value of 0% for RR and RD.

Core body temperature (°C) of the infant taken on admission to NICU or up to two hours after birth (Outcome 2.1)

One study reported this outcome in terms of core body temperature in °C (axillary) on admission to NICU before the infant was unwrapped (Bhavsar 2015).

Outcome 2.1.1: For infants at < 37 weeks' gestation with birth weight ≤ 2500 grams, data show a statistically significant difference for core body temperature on admission to the NICU favouring the intervention (plastic wrap) group when compared with the group that received routine care immediately after birth in the delivery room (MD 0.70°C, 95% CI 0.32 to 1.08; one study; N = 96) (Analysis 2.1).

Hypothermia on admission to NICU (core body temperature < 36.5°C or skin temperature < 36°C) (Outcome 2.2)

Bhavsar 2015, in addition to reporting core body temperature on admission to the NICU as a continuous variable, provided data in a dichotomous format in terms of the incidence of hypothermia among intervention and control groups (plastic wrap and routine care). Researchers defined hypothermia as core body temperature (axillary) < 35°C on admission to the NICU.

Outcome 2.2.1: For infants at < 37 weeks' gestation with birth weight ≤ 2500 grams, plastic wrap significantly reduced risk of hypothermia on admission to the NICU (RR 0.48, 95% CI 0.27 to 0.84; RD ‐0.27, 95% CI ‐0.45 to ‐0.08; one study; N = 96). Four infants would have to be wrapped in plastic to prevent one from becoming hypothermic (NNTB 4, 95% CI 2 to 13) (Analysis 2.2).

Decrease in core body temperature (°C) from baseline before transport to NICU admission (Outcome 2.3)

One study reported this outcome in terms of a decrease in core body temperature from baseline before transport to NICU admission (Bhavsar 2015). This was not a prespecified outcome at the review protocol stage.

Outcome 2.3.1: For infants at < 37 weeks' gestation with birth weight ≤ 2500 grams, data show a statistically significant difference in decreased temperature from baseline before transport favouring the intervention (plastic wrap) group when compared with the group that received routine care immediately after birth in the delivery room (MD ‐0.40°C, 95% CI ‐0.61 to ‐0.19; one study; N = 96) (Analysis 2.3).

Hyperthermia on admission to NICU: core body temperature > 37.5°C (Outcome 2.4)

Bhavsar 2015, in addition to reporting core body temperature on admission to the NICU as a continuous variable, provided data in a dichotomous format in terms of incidence of hyperthermia in the intervention and control groups (plastic wrap and routine care). Study authors defined hyperthermia as a core body temperature (axillary) > 37.5°C on admission to the NICU.

Outcome 2.4.1: For infants at < 37 weeks' gestation with birth weight ≤ 2500 grams, data show no significant differences in risk of hyperthermia on admission to the NICU between infants who received plastic wrap and those given routine care (RR 2.88, 95% CI 0.12 to 68.98; RD 0.02, 95% CI ‐0.03 to 0.08; one study; N = 96) (Analysis 2.4).

Base excess (Outcome 2.5)

One study reported this outcome in terms of base excess (Bhavsar 2015). Trial authors did not clearly state the measurement time point. This was not a prespecified outcome at the review protocol stage.

Outcome 2.5.1: For infants at < 37 weeks' gestation with birth weight ≤ 2500 grams, data show no statistically significant differences between the two intervention groups (plastic wrap and routine care) for base excess (MD 0.60, 95% CI ‐0.49 to 1.69; one study; N = 96) (Analysis 2.5).

Blood gas pH (Outcome 2.6)

One study reported this outcome in terms of blood gas pH (Bhavsar 2015). Researchers did not clearly state the measurement time point. This was not a prespecified outcome at the review protocol stage.

Outcome 2.6.1: For infants at < 37 weeks' gestation with birth weight ≤ 2500 grams, data show no statistically significant differences between the two intervention groups (plastic wrap and routine care) in blood gas pH (MD 0.00, 95% CI ‐0.02 to 0.02; one study; N = 96) (Analysis 2.6).

Duration of oxygen therapy (days) (Outcome 2.7)

One study reported this outcome in terms of duration of oxygen therapy (days) (Bhavsar 2015). This was not a prespecified outcome at the review protocol stage.

Outcome 2.7.1: For infants at < 37 weeks' gestation with birth weight ≤ 2500 grams, data show no statistically significant differences between the two interventions (plastic wrap and routine care) for duration of oxygen therapy (days) (MD ‐2.39, 95% CI ‐8.27 to 3.49; one study; N = 96) (Analysis 2.7).

Blood glucose level (mg/dL) within two hours of birth (Outcome 2.8)

One study reported this outcome in terms of results of hemo glucose tests (mg/dL) (Bhavsar 2015). This was not a prespecified outcome at the review protocol stage.

Outcome 2.8.1: For infants at < 37 weeks' gestation with birth weight ≤ 2500 grams, data show no statistically significant differences between the two interventions (plastic wrap and routine care) for blood glucose level within two hours of birth (MD 7.20, 95% CI ‐2.03 to 16.43; one study; N = 96) (Analysis 2.8).

Hypoglycaemia (blood glucose < 40 mg/dL) within two hours after birth (Outcome 2.9)

One study reported this outcome in terms of incidence of blood glucose < 40 mg/dL (2.3 mmol/L) within two hours after birth in intervention and control groups (plastic wrap and routine care) (Bhavsar 2015). This was not the prespecified definition of hypoglycaemia at the review protocol stage.

Outcome 2.9.1: For infants at < 37 weeks' gestation and birth weight ≤ 2500 grams, plastic wrap significantly reduced risk of hypoglycaemia within two hours after birth (RR 0.55, 95% CI 0.31 to 0.98; RD ‐0.20, 95% CI ‐0.39 to ‐0.02; one study; N = 96). Five infants would have to be wrapped in plastic to prevent one from becoming hypoglycaemic (NNTB 5, 95% CI 3 to 50) (Analysis 2.9).

Severe metabolic acidosis (Outcome 2.10)

One study reported this outcome in terms of incidence of pH < 7.20 and/or base deficit > 10 mmol/L within the first three days of life among intervention and control groups (plastic wrap and routine care) (Bhavsar 2015).

Outcome 2.10.1: For infants at < 37 weeks' gestation with birth weight ≤ 2500 grams, data show no significant differences in risk of severe metabolic acidosis within the first three days after birth between infants who received plastic wrap and those given routine care (RR 1.15, 95% CI 0.38 to 3.52; RD 0.02, 95% CI ‐0.11 to 0.14; one study; N = 96) (Analysis 2.10).

Core body temperature (°C) of the infant taken on admission to NICU or up to two hours after birth

One study reported this outcome in terms of time to achieve a mean core body temperature (axillary) of 36.5°C and core body temperature in °C (axillary) of the infant every 15 minutes until two hours after birth (Cardona Torres 2012). These were not prespecified outcomes at the review protocol stage. For the purposes of this review, we have reported core body temperature in °C (axillary) at 30 minutes, 1 hour, 90 minutes, and 2 hours after birth.

Core body temperature (°C) of the infant taken at 30 minutes after birth (Outcome 3.1)

One study reported this outcome in terms of core body temperature in °C (axillary) at 30 minutes after birth (Cardona Torres 2012). This was not a prespecified outcome at the review protocol stage.

Outcome 3.1.1: For infants at ≥ 28 and < 37 weeks' gestation and birth weight ≥ 1000 and ≤ 2499 grams, data show a statistically significant difference for core body temperature 30 minutes after birth favouring the intervention (plastic bag with previous drying) group when compared with the group that received routine care immediately after birth in the delivery room (MD 0.30°C, 95% CI 0.12 to 0.48; one study; N = 60) (Analysis 3.1).

Core body temperature (°C) of the infant taken at one hour after birth (Outcome 3.2)

One study reported this outcome in terms of core body temperature in °C (axillary) 60 minutes after birth (Cardona Torres 2012). This was not a prespecified outcome at the review protocol stage.

Outcome 3.2.1 For infants at ≥ 28 and < 37 weeks' gestation with birth weight ≥ 1000 and ≤ 2499 grams, data show a statistically significant difference for core body temperature 60 minutes after birth favouring the intervention (plastic bag with previous drying) group when compared with the group that received routine care immediately after birth in the delivery room (MD 0.30°C, 95% CI 0.11 to 0.49; one study; N = 60) (Analysis 3.2) (Cardona Torres 2012).

Core body temperature (°C) of the infant taken at 90 minutes after birth (Outcome 3.3)

One study reported this outcome in terms of core body temperature in °C (axillary) 90 minutes after birth (Cardona Torres 2012). This was not a prespecified outcome at the review protocol stage.

Outcome 3.3.1: For infants at ≥ 28 and < 37 weeks' gestation with birth weight ≥ 1000 and ≤ 2499 grams, data show a statistically significant difference for core body temperature 90 minutes after birth favouring the intervention (plastic bag with previous drying) group when compared with the group that received routine care immediately after birth in the delivery room (MD 0.30°C, 95% CI 0.12 to 0.48; one study' N = 60) (Analysis 3.3).

Core body temperature (°C) of the infant taken at two hours after birth (Outcome 3.4)

One study reported this outcome in terms of core body temperature in °C (axillary) 120 minutes after birth (Cardona Torres 2012). This was not a prespecified outcome at the review protocol stage.

Outcome 3.4.1: For infants at ≥ 28 and < 37 weeks' gestation with birth weight ≥ 1000 and ≤ 2499 grams, data show a statistically significant difference for core body temperature 120 minutes after birth favouring the intervention (plastic bag with previous drying) group when compared with the group that received routine care immediately after birth in the delivery room (MD 0.40°C, 95% CI 0.24 to 0.56; one study; N = 60) (Analysis 3.4).

Hypothermia on admission to the NICU (core body temperature < 36.5°C or skin temperature < 36°C) (Outcome 3.5)

One study reported this outcome in terms of incidence of hypothermia in the intervention and control groups (plastic bag with previous drying and routine care) (Cardona Torres 2012). However, investigators provided no clear definition of hypothermia.

Outcome 3.5.1: For infants at ≥ 28 and < 37 weeks' gestation with birth weight ≥ 1000 and ≤ 2499 grams, data show no significant difference in risk of hypothermia on admission to the NICU between infants who received plastic bag with previous drying and those given routine care (RR 0.09, 95% CI 0.01 to 1.57; RD ‐0.17, 95% CI ‐0.31 to ‐0.03; one study; N = 60) (Analysis 3.5).

Computational errors can occur one or both arms of a study have a zero count, as is the case in Cardona Torres 2012. RevMan software compensates by adding 0.5 to each cell.

Blood glucose concentration (mmol/L) 120 minutes after birth (Outcome 3.6)

One study reported this outcome (Cardona Torres 2012). When data were presented as mg/dL (USA Standard), we converted these to mmol/L (UK Standard). This was not a prespecified outcome at the review protocol stage.

Outcome 3.6.1: One study reported this outcome as a median value with interquartile range (IQR) (Cardona Torres 2012). For infants at ≥ 28 and < 37 weeks' gestation with birth weight ≥ 1000 and ≤ 2499 grams, median glucose concentrations at 120 minutes after birth were comparable in the intervention (plastic bag with previous drying) and control (routine care) groups (one study; N = 60: P > 0.05) (Analysis 3.6).

Core body temperature (°C) of the infant taken on admission to the NICU or up to two hours after birth (Outcome 4.1)

One study reported this outcome in terms of core body temperature in °C (axillary) on admission to the NICU (Trevisanuto 2010).

Outcome 4.1.1: For infants at < 29 weeks' gestation, data show a statistically significant difference for core body temperature on admission to the NICU favouring the intervention (plastic cap) group when compared with the group that received routine care immediately after birth in the delivery room (MD 0.80°C, 95% CI 0.41 to 1.19; one study; N = 64) (Analysis 4.1).

Hypothermia on admission to the NICU (core body temperature < 36.4°C) (Outcome 4.2)

Trevisanuto 2010 in addition to reporting core body temperature on admission to the NICU as a continuous variable, provided data in a dichotomous format in terms of incidence of hypothermia in the intervention and control groups (plastic cap and routine care). Investigators defined hypothermia as a core body temperature (axillary) < 36.4°C on admission to the NICU.

Outcome 4.2.1: For infants at < 29 weeks' gestation, plastic cap significantly reduced risk of hypothermia on admission to the NICU (RR 0.48, 95% CI 0.32 to 0.73; RD ‐0.47, 95% CI ‐0.67 to ‐0.27; one study; N = 64). This finding is consistent with those for Outcome measure 4.1.1. Two infants would have to wear a plastic cap to prevent one infant from becoming hypothermic (NNTB 2, 95% CI 2 to 4) (Analysis 4.2).

Outside the normothermic range on admission to the NICU or up to two hours after birth (Outcome 4.3)

We derived this outcome for one study in terms of incidence of core body temperature (axillary) outside the normothermic range in the intervention and control groups (plastic cap and routine care) (Trevisanuto 2010). Investigators defined normothermic range as core body temperature (axillary) within the range 36.4°C to 37.5°C on admission to the NICU. This was not a prespecified outcome at the review protocol stage.

Outcome 4.3.1: For infants at < 29 weeks' gestation, plastic cap significantly reduced the risk of having a core body temperature outside the normothermic range on admission to the NICU (RR 0.48, 95% CI 0.32 to 0.73; RD ‐0.47, 95% CI ‐0.67 to ‐0.27; one study; N = 64). Two infants would have to receive a plastic cap to prevent one infant from having a core body temperature outside the normothermic range on admission to the NICU (NNTB 2, 95% CI 2 to 4) (Analysis 4.3).

Core body temperature taken one hour after initial admission temperature to the NICU was taken (Outcome 4.4)

One study reported this outcome in terms of core body temperature in °C (axillary) taken one hour after the initial NICU admission was taken (Trevisanuto 2010). This was not a prespecified outcome at the review protocol stage.

Outcome 4.4.1: For infants at < 29 weeks' gestation, data show a statistically significant difference for core body temperature taken one hour after initial NICU admission temperature was taken favouring the intervention (plastic cap) group when compared with the group that received routine care immediately after birth in the delivery room (MD 0.80°C, 95% CI 0.46 to 1.14; one study; N = 64) (Analysis 4.4).

Major brain injury (defined as sonographic evidence of IVH with ventricular dilatation, parenchymal haemorrhagic infarction, or periventricular leukomalacia) (Outcome 4.5)

One study reported this outcome in terms of incidence of major brain injury (defined as sonographic evidence of IVH with ventricular dilatation, parenchymal haemorrhagic infarction, or periventricular leukomalacia) in intervention and control groups (plastic cap and routine care) (Trevisanuto 2010). This was not a prespecified outcome at the review protocol stage.

Outcome 4.5.1: For infants at < 29 weeks' gestation, data show no significant difference in risk of major brain injury between infants who received plastic cap and those given routine care (RR 1.50, 95% CI 0.27 to 8.38; RD 0.03, 95% CI ‐0.10 to 0.16; one study; N = 64) (Analysis 4.5).

Mortality (death within hospital stay) (Outcome 4.6)

One study reported this outcome in terms of incidence of death within hospital stay in intervention and control groups (plastic cap and routine care) (Trevisanuto 2010).

Outcome 4.6.1: For infants at < 29 weeks' gestation, data show no significant differences in risk of death within hospital stay between infants who received plastic cap and those given routine care (RR 1.50, 95% CI 0.27 to 8.38; RD 0.03, 95% CI ‐0.10 to 0.16; one study; N = 64) (Analysis 4.6).

Bicarbonate (mmol/L) (Outcome 4.7)

One study reported this outcome (Trevisanuto 2010). This was not a prespecified outcome at the review protocol stage.

Outcome 4.7.1: For infants at < 29 weeks' gestation, data show no statistically significant differences between the two interventions (plastic cap and routine care) for bicarbonate (MD 1.00 mmol/L, 95% CI ‐0.25 to 2.25; one study; N = 64) (Analysis 4.7).

Blood gas pH (first) (Outcome 4.8)

One study reported this outcome in terms of first blood pH (Trevisanuto 2010). This was not a prespecified outcome at the review protocol stage.

Outcome 4.8.1: For infants at < 29 weeks' gestation, data show no statistically significant differences between the two interventions (plastic cap and routine care) for first blood gas pH (MD 0.01, 95% CI ‐0.03 to 0.05; one study; N = 64) (Analysis 4.8). Because pH is on a logarithmic scale, it would be more appropriate to measure this outcome as a median value and range or IQR, or to avoid its use as a continuous variable such as that prespecified at the review protocol stage: severe metabolic acidosis defined as pH < 7.20 and/or base deficit > 10 mmol/L within the first three days of life.

First serum glucose concentration (mmol/L) on admission to the NICU (Outcome 4.9)

One study reported this outcome in terms of first serum glucose concentration (mmol/L) on admission to the NICU (Trevisanuto 2010). This was not a prespecified outcome at the review protocol stage.

Outcome 4.9.1: For infants at < 29 weeks' gestation, data show no statistically significant differences between the two interventions (plastic cap and routine care) for first serum glucose concentration (MD 0.10 mmol/L, 95% CI ‐0.42 to 0.62; one study; N = 64 (Analysis 4.9).

Intubation at birth (Outcome 4.10)

One study reported this outcome in terms of incidence of intubation at birth in the intervention and control groups (plastic cap and routine care) (Trevisanuto 2010).

Outcome 4.10.1: For infants at < 29 weeks' gestation, data show no significant differences in risk of intubation at birth between infants who received plastic cap and those given routine care (RR 0.82, 95% CI 0.49 to 1.37; RD ‐0.09, 95% CI ‐0.34 to 0.15; one study; N = 64) (Analysis 4.10).

Core body temperature (°C) of the infant taken on admission to the NICU or up to two hours after birth (Outcome 5.1)

Two studies comprising 122 infants reported this outcome in terms of core body temperature in °C (axillary) at the 10th, 15th, 30th, and 60th minutes of life (Tescon‐delos Santos 2012), as well as upon admission to the NICU (Talakoub 2015; Tescon‐delos Santos 2012), and at one and two hours after the initial NICU admission temperature was taken (Tescon‐delos Santos 2012). Each individual study showed a significant effect ‐ as in Talakoub 2015 ‐ or provided data tending towards favouring the intervention (plastic wrap or bag) ‐ as in Tescon‐delos Santos 2012.

Outcome 5.1.1: For infants at ≥ 28 and ≤ 36 weeks' gestation, data show a statistically significant difference for core body temperature on admission to the NICU favouring the intervention (plastic bag + plastic cap) group when compared with the group that received routine care immediately after birth in the delivery room (MD 0.32°C, 95% CI 0.15 to 0.50; two studies; N = 122) (Analysis 5.1).

The test for homogeneity failed with an I² value of 90% (high heterogeneity). This heterogeneity could possibly be attributed to differences in included gestational ages at ≥ 28 and ≤ 32 weeks ‐ as in Talakoub 2015 ‐ and at ≥ 28 and ≤ 36 weeks ‐ as in Tescon‐delos Santos 2012.

Core body temperature (°C) of the infant taken at the 10th minute of life (Outcome 5.2)

One study reported this outcome in terms of core body temperature in °C (axillary) at the 10th minute of life (Tescon‐delos Santos 2012).

Outcome 5.2.1: For infants at ≥ 28 and ≤ 36 weeks' gestation, data show no statistically significant differences between the two interventions (plastic bag + plastic cap and routine care) for core body temperature at the 10th minute of life (MD ‐0.27°C, 95% CI ‐0.55 to 0.01; one study; N = 58) (Analysis 5.2).

Core body temperature (°C) of the infant taken at the 15th minute of life (Outcome 5.3)

One study reported this outcome in terms of core body temperature in °C (axillary) at the 15th minute of life (Tescon‐delos Santos 2012).

Outcome 5.3.1: For infants at ≥ 28 and ≤ 36 weeks' gestation, data show no statistically significant differences between the two interventions (plastic bag + plastic cap and routine care) for core body temperature at the 15th minute of life (MD ‐0.26°C, 95% CI ‐0.56 to 0.05; one study; N = 58) (Analysis 5.3).

Core body temperature (°C) of the infant taken at the 30th minute of life (Outcome 5.4)

One study reported this outcome in terms of core body temperature in °C (axillary) at the 30th minute of life (Tescon‐delos Santos 2012).

Outcome 5.4.1: For infants at ≥ 28 and ≤ 36 weeks' gestation, data show no statistically significant differences between the two interventions (plastic bag + plastic cap and routine care) for core body temperature (axillary °C) at the 30th minute of life (MD 0.06°C, 95% CI ‐0.23 to 0.35; one study; N = 58) (Analysis 5.4).

Core body temperature (°C) of the infant taken at one hour of life (Outcome 5.5)

One study reported this outcome in terms of core body temperature in °C (axillary) at one hour of life (Tescon‐delos Santos 2012).

Outcome 5.5.1: For infants at ≥ 28 and ≤ 36 weeks' gestation, data show no statistically significant differences between the two interventions (plastic bag + plastic cap and routine care) for core body temperature (axillary °C) at one hour of life (MD ‐0.02°C, 95% CI ‐0.32 to 0.27; one study; N = 58) (Analysis 5.5).

Core body temperature (°C) of the infant taken at one hour after the initial NICU admission temperature was taken (Outcome 5.6)

One study reported this outcome in terms of core body temperature in °C (axillary) one hour after the initial NICU temperature was taken (Talakoub 2015).

Outcome 5.6.1: For infants at ≥ 28 and ≤ 32 weeks' gestation, data show a statistically significant difference for core body temperature one hour after the initial NICU admission temperature was taken favouring the intervention (plastic bag + plastic cap) group when compared with the group that received routine care immediately after birth in the delivery room (MD 0.83°C, 95% CI 0.37 to 1.29; one study; N = 64) (Analysis 5.6).

Core body temperature (°C) of the infant taken at two hours after the initial NICU admission temperature was taken (Outcome 5.7)

One study reported this outcome in terms of core body temperature in °C (axillary) two hours after the initial NICU admission temperature was taken (Talakoub 2015).

Outcome 5.7.1: For infants at ≥ 28 and ≤ 32 weeks' gestation, data show a statistically significant difference for core body temperature two hours after the initial NICU admission temperature was taken favouring the intervention (plastic bag + plastic cap) group when compared with the group that received routine care immediately after birth in the delivery room (MD 1.11°C, 95% CI 0.65 to 1.57; one study; N = 64) (Analysis 5.7).

Hyperthermia (core body temperature > 37.0°C on admission to the NICU (Outcome 5.8)

Two studies comprising 122 infants reported this outcome (Talakoub 2015; Tescon‐delos Santos 2012). Tescon‐delos Santos 2012, in addition to reporting core body temperature on admission to the NICU as a continuous variable, provided data in a dichotomous format in terms of incidence of hyperthermia in the intervention and control groups (plastic bag + plastic cap and routine care). Investigators defined hyperthermia as a core body temperature (axillary) > 37.0°C on admission to the NICU. Talakoub 2015 did not provide a clear definition for hyperthermia but reported no hyperthermia in either group.

Outcome 5.8.1: For infants at ≥ 28 and ≤ 36 weeks' gestation, data show no significant difference in risk of hyperthermia between infants who received plastic bag + plastic cap and those given routine care (typical RR 0.18, 95% CI 0.02 to 1.39; typical RD ‐0.08, 95% CI ‐0.16 to 0.00; one study; N = 122) (Analysis 5.8).

The test for homogeneity failed with an I² value of 87% (high heterogeneity) for RD. This heterogeneity could possibly be attributed to differences in included gestational ages at ≥ 28 and ≤ 32 weeks ‐ in Talakoub 2015 ‐ and at ≥ 28 and ≤ 36 weeks ‐ in Tescon‐delos Santos 2012.

Hyponatraemia (Outcome 5.9)

One study reported this outcome in terms of incidence of serum sodium concentration < 130 mmol/L in intervention and control groups (plastic bag + plastic cap and routine care) (Tescon‐delos Santos 2012).

Outcome 5.9.1: For infants at ≥ 28 and ≤ 36 weeks' gestation, data show no significant differences in risk of hyponatraemia between infants who received plastic bag + plastic cap and those given routine care (RR 1.43, 95% CI 0.35 to 5.83; RD 0.04, 95% CI ‐0.13 to 0.21; one study; N = 58) (Analysis 5.9).

Weight (grams) at fifth day of life (Outcome 5.10)

One study reported this outcome in terms of weight (grams) on the fifth day of life or the last day of life if death occurred before the fifth day (Tescon‐delos Santos 2012). This outcome measure was designed to assess whether an infant had greater than 20% body weight loss by the fifth day of life. This was not a prespecified outcome at the review protocol stage.

Outcome 5.10.1: For infants at ≥ 28 and ≤ 36 weeks' gestation, data show no statistically significant differences between the two interventions (plastic bag + plastic cap and routine care) for weight (grams) on the fifth day of life (MD ‐74.20 g, 95% CI ‐301.63 to 153.23; one study; N = 58) (Analysis 5.10).

Outcome 5.10.2: For infants at ≥ 28 and ≤ 36 weeks' gestation, data show no reported cases when the infant lost more than 20% body weight by the fifth day of life.

Core body temperature (°C) of the infant taken on admission to the NICU or up to two hours after birth

One study reported this outcome in terms of time to achieve a mean core body temperature (axillary) of 36.5°C and core body temperature in °C (axillary) of the infant every 15 minutes until two hours after birth (Cardona Torres 2012). These were not prespecified outcomes at the review protocol stage. For the purposes of this review, we have reported core body temperature in °C (axillary) at 30 minutes, 1 hour, 90 minutes, and 2 hours after birth

Core body temperature (°C) 30 minutes after birth (Outcome 6.1)

One study reported this outcome in terms of core body temperature in °C (axillary) 30 minutes after birth (Cardona Torres 2012). This was not a prespecified outcome at the review protocol stage.

Outcome 6.1.1: For infants at ≥ 28 and < 37 weeks' gestation with birth weight ≥ 1000 and ≤ 2499 grams, data show no statistically significant differences between the two interventions (plastic bag with previous drying vs plastic bag without previous drying) for core body temperature 30 minutes after birth (MD 0.0°C, 95% CI ‐0.17 to 0.17; one study; N = 60) (Analysis 6.1).

Core body temperature (°C) of the infant taken at one hour after birth (Outcome 6.2)

One study reported this outcome in terms of core body temperature in °C (axillary) 60 minutes after birth (Cardona Torres 2012). This was not a prespecified outcome at the review protocol stage.

Outcome 6.2.1: For infants at ≥ 28 and < 37 weeks' gestation with birth weight ≥ 1000 and ≤ 2499 grams, data show no statistically significant differences between the two interventions (plastic bag with previous drying vs plastic bag without previous drying) for core body temperature 60 minutes after birth (MD ‐0.10 °C, 95% CI ‐0.28 to 0.08; one study; N = 60) (Analysis 6.2).

Core body temperature (°C) of the infant taken at 90 minutes after birth (Outcome 6.3)

One study reported this outcome in terms of core body temperature in °C (axillary) 90 minutes after birth (Cardona Torres 2012). This was not a prespecified outcome at the review protocol stage.

Outcome 6.3.1: For infants at ≥ 28 and < 37 weeks' gestation with birth weight ≥ 1000 and ≤ 2499 grams, data show no statistically significant differences between the two interventions (plastic bag with previous drying vs plastic bag without previous drying) for core body temperature 90 minutes after birth (MD ‐0.10°C, 95% CI ‐0.29 to 0.09; one study; N = 60) (Analysis 6.3).

Core body temperature (°C) of the infant taken at two hours after birth (Outcome 6.4)

One study reported this outcome in terms of core body temperature in °C (axillary) 120 minutes after birth (Cardona Torres 2012). This was not a prespecified outcome at the review protocol stage.

Outcome 6.4.1: For infants at ≥ 28 and < 37 weeks' gestation with birth weight ≥ 1000 and ≤ 2499 grams, data show no statistically significant differences between the two interventions (plastic bag with previous drying vs plastic bag without previous drying) for core body temperature 120 minutes after birth (MD 0.10°C, 95% CI ‐0.04 to 0.24; one study; N = 60) (Analysis 6.4).

Hyperthermia on admission to the NICU: core body temperature > 37.5°C (Outcome 6.5)

Cardona Torres 2012, in addition to reporting core body temperature on admission to the NICU as a continuous variable, provided data in a dichotomous format in terms of incidence of hyperthermia in the intervention and comparison groups (plastic bag with previous drying vs plastic bag without previous drying). Investigators did not provide a clear definition of hyperthermia. Data show one case of hyperthermia (definition not reported) in the plastic bag without previous drying group (37.7°C).

Outcome 6.5.1: For infants at ≥ 28 and < 37 weeks' gestation with birth weight ≥ 1000 and ≤ 2499 grams, data show no significant differences in risk of hyperthermia between infants who received plastic bag with previous drying and those given plastic bag without previous drying (RR 0.33, 95% CI 0.01 to 7.87; RD ‐0.03, 95% CI ‐0.12 to 0.05; one study; N = 60) (Analysis 6.5).

Blood glucose concentration (mmol/L) at 120 minutes after birth (Outcome 6.6)

One study reported this outcome as a median value with IQR (Cardona Torres 2012). Data were converted to the International System of Units (SI) mmol/L from mg/dL. This was not a prespecified outcome at the review protocol stage.

Outcome 6.6.1: For infants at ≥ 28 and < 37 weeks' gestation with birth weight ≥ 1000 and ≤ 2499 grams, median blood glucose concentrations at 120 minutes after birth were comparable in the intervention (plastic bag with drying) and active comparator groups (plastic bag without drying) (one study; N = 60; P > 0.05) (Analysis 6.6).

Core body temperature (°C) of the infant taken on admission to the NICU or up to two hours after birth (Outcome 7.1)

One study reported this outcome in terms of core body temperature in °C (axillary) on admission to the NICU (Trevisanuto 2010).

Outcome 7.1.1: For infants at < 29 weeks' gestation, data show no statistically significant differences between the two interventions (plastic cap and plastic bag) for core body temperature on admission to the NICU (MD 0.30°C, 95% CI ‐0.12 to 0.72; one study; N = 64) (Analysis 7.1).

Hypothermia on admission to the NICU (core body temperature < 36.4°C) (Outcome 7.2)

Trevisanuto 2010, in addition to reporting core body temperature on admission to the NICU as a continuous variable, provided data in a dichotomous format in terms of incidence of hypothermia in the intervention and comparison groups (plastic cap and plastic bag). Investigators defined hypothermia as a core body temperature (axillary) < 36.4°C on admission to the NICU.

Outcome 7.2.1: For infants at < 29 weeks' gestation, data show no significant differences in risk of hypothermia on admission to the NICU between infants who received plastic cap and those given plastic bag (RR 0.70, 95% CI 0.43 to 1.13; RD ‐0.19, 95% CI ‐0.43 to 0.05; one study; N = 64) (Analysis 7.2).

Outside normothermic range on admission to the NICU or up to two hours after birth (Outcome 7.3)

We derived this outcome for one study in terms of incidence of core body temperature (axillary) outside the normothermic range of 36.4°C to 37.5°C on admission to the NICU among intervention and comparison groups (plastic cap and plastic bag) (Trevisanuto 2010). This was not a prespecified outcome at the review protocol stage.

Outcome 7.3.1: For infants at < 29 weeks' gestation, data show no significant difference (borderline) in risk of having a core body temperature outside the normothermic range on admission to the NICU between infants who received plastic cap and those given plastic bag (RR 0.64, 95% CI 0.40 to 1.01; RD ‐0.25, 95% CI ‐0.49 to ‐0.01; one study; N = 64) (Analysis 7.3).

Core body temperature taken one hour after initial NICU admission temperature was taken (Outcome 7.4)

One study reported this outcome in terms of core body temperature in °C (axillary) (Trevisanuto 2010). This was not a prespecified outcome at the review protocol stage.

Outcome 7.4.1: For infants at < 29 weeks' gestation, data show a borderline statistically significant difference for core body temperature taken one hour after the initial NICU admission temperature was taken favouring the intervention (plastic cap) group when compared with the group that received plastic bag immediately after birth in the delivery room (MD 0.30°C, 95% CI 0.00 to 0.60; one study; N = 64) (Analysis 7.4).

Hyperthermia on admission to the NICU: core body temperature > 37.5°C (Outcome 7.5)

Trevisanuto 2010, in addition to reporting core body temperature on admission to the NICU as a continuous variable, provided data in a dichotomous format in terms of incidence of hyperthermia among intervention and comparison groups (plastic cap and plastic bag). Investigators defined hyperthermia as a core body temperature (axillary) > 37.5°C on admission to the NICU.

Outcome 7.5.1: For infants at < 29 weeks' gestation, data show no significant difference in risk of hyperthermia on admission to the NICU between infants who received plastic cap and those given plastic bag (RR 0.20, 95% CI 0.01 to 4.01; RD ‐0.06, 95% CI ‐0.16 to 0.04; one study; N = 60) (Analysis 7.5).

Major brain injury (defined as sonographic evidence of IVH with ventricular dilatation, parenchymal haemorrhagic infarction, or periventricular leukomalacia) (Outcome 7.6)

One study reported this outcome in terms of incidence of major brain injury defined as sonographic evidence of IVH with ventricular dilatation, parenchymal haemorrhagic infarction, or periventricular leukomalacia in the intervention and comparison groups (plastic cap and plastic bag) (Trevisanuto 2010). This was not a prespecified outcome at the review protocol stage.

Outcome 7.6.1: For infants at < 29 weeks' gestation, data show no significant difference in risk of major brain injury between infants who received plastic cap and those given plastic bag (RR 1.50, 95% CI 0.27 to 8.38; RD 0.03, 95% CI ‐0.10 to 0.16; one study; N = 64) (Analysis 7.6).

Mortality (death within hospital stay) (Outcome 7.7)

One study reported this outcome in terms of incidence of death within hospital stay in the intervention and comparison groups (plastic cap and plastic bag) (Trevisanuto 2010).

Outcome 7.7.1: For infants at < 29 weeks' gestation, data show no significant difference in risk of death within hospital stay between infants who received plastic cap and those given plastic bag (RR 1.50, 95% CI 0.27 to 8.38; RD 0.03, 95% CI ‐0.10 to 0.16; one study; N = 64) (Analysis 7.7).

Bicarbonate concentration (mmol/L) (Outcome 7.8)

One study reported this outcome in terms of bicarbonate concentration (mmol/L) (Trevisanuto 2010). This was not a prespecified outcome at the review protocol stage.

Outcome 7.8.1: For infants at < 29 weeks' gestation, data show a borderline statistically significant difference for bicarbonate concentration favouring the intervention (plastic cap) group when compared with the group that received plastic bag immediately after birth in the delivery room (MD 1.00 mmol/L, 95% CI 0.02 to 1.98; one study; N = 64) (Analysis 7.8).

Blood gas pH (first) (Outcome 7.9)

One study reported this outcome in terms of first blood gas pH (Trevisanuto 2010). This was not a prespecified outcome at the review protocol stage. Because pH is on a logarithmic scale, it would be more appropriate to measure this outcome as a median value with range or IQR, or to avoid its use as a continuous variable such as those prespecified at the review protocol stage: severe metabolic acidosis as defined by pH < 7.20 and/or base deficit > 10 mmol/L within the first three days of life.

Outcome 7.9.1: For infants at < 29 weeks' gestation, data show no statistically significant differences between the two interventions (plastic cap and plastic bag) for first blood gas pH (MD ‐0.02, 95% CI ‐0.06 0.02; one study, n = 64) (Analysis 7.9).

First serum glucose concentration (mmol/L) (Outcome 7.10)

One study reported this outcome in terms of first serum glucose concentration (mmol/L) on admission to the NICU (Trevisanuto 2010).

Outcome 7.10.1: For infants at < 29 weeks' gestation, data show no statistically significant differences between the two interventions (plastic cap and plastic bag) for first serum glucose concentration on admission to the NICU (MD 0.00 mmol/L, 95% CI, ‐0.50 to 0.50; one study; N = 64) (Analysis 7.10).

Intubation at birth (Outcome 7.11)

One study reported this outcome in terms of incidence of intubation at birth in the intervention and comparison groups (plastic cap and plastic bag) (Trevisanuto 2010).

Outcome 7.11.1: For infants at < 29 weeks' gestation, data show no significant difference in risk of intubation at birth between infants who received plastic cap and those given plastic bag (RR 0.82, 95% CI 0.49 to 1.37; RD ‐0.09, 95% CI ‐0.34 to 0.15; one study; N = 64) (Analysis 7.11).

Core body temperature (°C) of the infant taken on admission to the NICU or up to two hours after birth

One study reported this outcome in terms of core body temperature in °C (axillary) at 20, 40, and 60 minutes after birth and decrease in core body temperature during the first hour after birth (Caglar 2014).

Core body temperature (°C) of the infant taken at 20 minutes after birth (Outcome 8.1)

Outcome 8.1.1: For infants at ≤ 32 weeks' gestation, data show a statistically significant difference for core body temperature taken at 20 minutes after birth favouring the intervention (plastic bag) group when compared with the group that received plastic wrap immediately after birth in the delivery room (MD 0.14°C, 95% CI 0.08 to 0.20; one study; N = 59) (Analysis 8.1).

Core body temperature (°C) of the infant taken at 40 minutes after birth (Outcome 8.2)

Outcome 8.2.1: For infants at ≤ 32 weeks' gestation, data show a statistically significant difference for core body temperature taken at 40 minutes after birth favouring the intervention (plastic bag) group when compared with the group that received plastic wrap immediately after birth in the delivery room (MD 0.30°C, 95% CI 0.24 to 0.36; one study; N = 59) (Analysis 8.2).

Core body temperature (°C) of the infant taken at one hour after birth (Outcome 8.3)

Outcome 8.3.1: For infants at ≤ 32 weeks' gestation, data show a statistically significant difference for core body temperature taken at one hour after birth favouring the intervention (plastic bag) group when compared with the group that received plastic wrap immediately after birth in the delivery room (MD 0.35°C, 95% CI 0.29 to 0.41; one study; N = 59) (Analysis 8.3).

Decrease in core body temperature (°C) of the infant during one hour after birth (Outcome 8.4)

Outcome 8.4.1: For infants at ≤ 32 weeks' gestation, data show a statistically significant difference for decrease in core body temperature during the first hour after birth favouring the intervention (plastic bag) group when compared with the group that received plastic wrap immediately after birth in the delivery room (MD ‐1.34°C, 95% CI ‐2.22 to ‐0.46; one study; N = 59) (Analysis 8.4).

Hypothermia within one hour after birth (core body temperature < 36.5°C or skin temperature < 36°C) (Outcome 8.5)

Caglar 2014, in addition to reporting core body temperature on admission to NICU as a continuous variable, provided data in a dichotomous format in terms of incidence of hypothermia in the intervention and comparison groups (plastic bag and plastic wrap). Investigators defined hypothermia as core body temperature (axillary) < 36.4°C; cold stress as 36°C to 36.4°C; moderate hypothermia as 32°C to 35.9°C; and severe hypothermia as < 32°C.

Outcome 8.5.1: For infants at ≤ 32 weeks' gestation, data show no significant difference in risk of hypothermia within one hour after birth between infants who received plastic bags and those given plastic wrap (RR 0.84, 95% CI 0.63 to 1.12; RD ‐0.14, 95% CI ‐0.35 to 0.08; one study; N = 59) (Analysis 8.5).

Moderate hypothermia within one hour after birth (core body temperature 32°C to 35.9°C, or skin temperature 31.5°C to 35.4°C) (Outcome 8.6)

One study reported this outcome in terms of incidence of hypothermia in the intervention and comparison groups (plastic bag and plastic wrap) (Caglar 2014). Investigators defined moderate hypothermia as core body temperature within the range 32°C to 35.9°C.

Outcome 8.6.1: For infants at ≤ 32 weeks' gestation, data show no significant difference (borderline) in risk of hypothermia within one hour after birth between infants who received plastic bag and those given plastic wrap (RR 0.56, 95% CI 0.31 to 1.02; RD ‐0.29, 95% CI ‐0.54 to ‐ 0.03; one study; N = 59) (Analysis 8.6).

Outside normothermic range on admission to the NICU or up to two hours after birth (Outcome 8.7)

One study reported this outcome in terms of incidence of core body temperature (axillary) outside the normothermic range in intervention and comparison groups (plastic bag and plastic wrap) (Caglar 2014). Investigators defined the range of normothermia as core body temperature (axillary) within the range 36.5°C to 37.5°C within one hour after birth. This was not a prespecified outcome at the review protocol stage.

Outcome 8.7.1: For infants at ≤ 32 weeks' gestation, data show no significant difference in risk of having a core body temperature outside the normothermic range within one hour after birth between infants who received plastic bag and those given plastic wrap (RR 0.84, 95% CI 0.63 to 1.12; RD ‐0.14, 95% CI ‐0.35 to 0.08; one study; N = 59) (Analysis 8.7).

Core body temperature (°C) of the infant taken on admission to the NICU or up to two hours after birth (Outcome 9.1)

One study reported this outcome in terms of core body temperature in °C (axillary) on admission to the NICU (Doglioni 2014).

Outcome 9.1.1: For infants at < 29 weeks' gestation, data show no statistically significant differences between the two interventions (plastic total body wrap and plastic wrap, head uncovered) for core body temperature on admission to the NICU (MD 0.10°C, 95% CI ‐0.18 to 0.38; one study; N = 100) (Analysis 9.1).

Hypothermia on admission to the NICU (core body temperature < 36.5°C or skin temperature < 36°C) (Outcome 9.2)

Doglioni 2014, in addition to reporting core body temperature on admission to the NICU as a continuous variable, provided data in a dichotomous format in terms of incidence of hypothermia in the intervention and comparison groups (plastic total body wrap and plastic wrap, head uncovered). Investigators defined hypothermia as a core body temperature (axillary) < 36.5°C; mild hypothermia as 36°C to 36.4°C; and moderate hypothermia as 32°C to 35.9°C on admission to the NICU.

Outcome 9.2.1: For infants at < 29 weeks' gestation, data show no significant difference in risk of hypothermia on admission to the NICU between infants who received plastic total body wrap and those given plastic wrap (head uncovered) (RR 0.87, 95% CI 0.55 to 1.37; RD ‐0.06, 95% CI ‐0.25 to 0.13; one study; N = 100) (Analysis 9.2).

Mild hypothermia on admission to the NICU (core body temperature 32ºC to 35.9ºC) (Outcome 9.3)

Outcome 9.3.1: For infants at < 29 weeks' gestation, data show no significant difference in risk of mild hypothermia on admission to the NICU between infants who received plastic total body wrap and those given plastic wrap (head uncovered) (RR 1.08, 95% CI 0.56 to 2.05; RD 0.02, 95% CI ‐0.15 to 0.19; one study; N = 100) (Analysis 9.3).

Moderate hypothermia on admission to the NICU (core body temperature 32ºC to 35.9ºC) (Outcome 9.4)

Outcome 9.4.1: For infants at < 29 weeks' gestation, data show no significant difference in risk of moderate hypothermia on admission to the NICU between infants who received plastic total body wrap and those given plastic wrap (head uncovered) (RR 0.60, 95% CI 0.24 to 1.53; RD ‐0.08, 95% CI ‐0.22 to 0.06; one study; N = 100) (Analysis 9.4).

Outside the normothermic range on admission to the NICU or within two hours after birth (Outcome 9.5)

We derived this outcome from one study in terms of incidence of core body temperature (axillary) outside the normothermic range of 36.5°C to 37.5°C on admission to the NICU in the intervention and comparison groups (plastic total body wrap and plastic wrap, head uncovered) (Doglioni 2014 ). This was not a prespecified outcome at the review protocol stage.

Outcome 9.5.1: For infants at < 29 weeks' gestation, data show no significant difference in risk of having a core body temperature outside the normothermic range on admission to the NICU between infants who received plastic total body wrap and those given plastic wrap (head uncovered) (RR 0.88, 95% CI 0.59 to 1.32; RD ‐0.06, 95% CI ‐0.26 to 0.14; one study; N = 100) (Analysis 9.5).

Core body temperature (°C) of the infant taken one hour after admission to the NICU (Outcome 9.6)

One study reported this outcome in terms of core body temperature in °C (axillary) one hour after admission to the NICU (Doglioni 2014).

Outcome 9.6.1: For infants at < 29 weeks' gestation, data show no statistically significant difference between the two interventions (plastic total body wrap and plastic wrap, head uncovered) for core body temperature one hour after admission to the NICU (MD ‐0.10°C, 95% CI ‐0.47 to 0.27; one study; N = 100) (Analysis 9.6).

Hyperthermia on admission to the NICU (core body temperature > 37.5°C) (Outcome 9.7)

Doglioni 2014, in addition to reporting core body temperature on admission to the NICU as a continuous variable, provided data in a dichotomous format in terms of incidence of hyperthermia in the intervention and comparison groups (plastic total body wrap and plastic wrap, head uncovered). Investigators defined hyperthermia as core body temperature (axillary) > 37.5°C.

Outcome 9.7.1: For infants at < 29 weeks' gestation, data show no significant difference in risk of hyperthermia on admission to the NICU after birth between infants who received plastic total body wrap and those given plastic wrap (head uncovered) (RR 1.00, 95% CI 0.21 to 4.72; RD 0.00, 95% CI ‐0.09 to 0.09; one study; N = 100) (Analysis 9.7). One infant in the wrap group had an axillary temperature > 38°C.

Major brain injury

One study reported this outcome in terms of incidence of major brain injury in the intervention and comparison groups (plastic total body wrap and plastic wrap, head uncovered), as defined by sonographic evidence of IVH with ventricular dilatation, parenchymal haemorrhagic infarction, or periventricular leukomalacia (Doglioni 2014).

Major brain injury: intraventricular haemorrhage (IVH) (Outcome 9.8)

One study reported this outcome in terms of incidence of severe IVH in the intervention and comparison groups (plastic total body wrap and plastic wrap, head uncovered) (Doglioni 2014).

Outcome 9.8.1: For infants at < 29 weeks' gestation, data show no significant difference in risk of severe IVH between infants who received plastic total body wrap and those given plastic wrap (head uncovered) (RR 0.80, 95% CI 0.34 to 1.86; RD ‐0.04, 95% CI ‐0.19 to 0.11; one study; N = 100) (Analysis 9.8).

Major brain injury: periventricular leukomalacia (PVL) (Outcome 9.9)

One study reported this outcome in terms of incidence of severe PVL in intervention and comparison groups (plastic total body wrap and plastic wrap, head uncovered) (Doglioni 2014).

Outcome 9.9.1: For infants at < 29 weeks' gestation, data show no significant difference in risk of PVL between infants who received plastic total body wrap and those given plastic wrap (head uncovered) (RR 1.00, 95% CI 0.06 to 15.55; RD 0.00, 95% CI ‐0.05 to 0.05; one study; N = 100) (Analysis 9.9).

Mortality (death within hospital stay or at six months' corrected gestation) (Outcome 9.10)

One study reported this outcome in terms of incidence of death before discharge from hospital or at six months' corrected gestation in the intervention and comparison groups (plastic total body wrap and plastic wrap, head uncovered) (Doglioni 2014).

Outcome 9.10.1: For infants at < 29 weeks' gestation, data show no significant difference in risk of death between infants who received plastic total body wrap and those given plastic wrap (head uncovered) (RR 0.29, 95% CI 0.06 to 1.31; RD ‐ 0.10, 95% CI ‐0.21 to 0.01; one study; N = 100) (Analysis 9.10).

Bronchopulmonary dysplasia (BPD) (Outcome 9.11)

One study reported this outcome in terms of incidence of oxygen dependency at 36 postconceptional weeks in the intervention and comparison groups (plastic total body wrap and plastic wrap, head uncovered) (Doglioni 2014 ). Investigators defined BPD as chronic lung disease at the review protocol stage.

Outcome 9.11.1: For infants at < 29 weeks' gestation, data show no significant difference in risk of BPD between infants who received plastic total body wrap and those given plastic wrap (head uncovered) (RR 1.00, 95% CI 0.59 to 1.69; RD 0.00, 95% CI ‐0.19 to 0.19; one study; N = 100) (Analysis 9.11).

Necrotising enterocolitis (NEC) (Outcome 9.12)

One study reported this outcome in terms of incidence of NEC in the intervention and comparison groups (plastic total body wrap and plastic wrap, head uncovered) (Doglioni 2014).

Outcome 9.12.1: For infants at < 29 weeks' gestation, data show no significant difference in the risk of NEC between infants who received plastic total body wrap and those given plastic wrap (head uncovered) (RR 1.00, 95% CI 0.41 to 2.46; RD 0.00, 95% CI ‐0.14 to 0.14; one study; N = 100) (Analysis 9.12).

Core body temperature (°C) of the infant taken on admission to the NICU or up to two hours after birth (Outcome 10.1)

One study reported this outcome in terms of core body temperature in °C (axillary) on admission to the NICU (Talakoub 2015).

Outcome 10.1.1: For infants at ≥ 28 and ≤ 32 weeks' gestation, data show a statistically significant difference in core body temperature on admission to the NICU favouring the intervention (plastic bag + plastic hat) group when compared with the group given plastic bag + cotton hat immediately after birth in the delivery room (MD 0.32°C, 95% CI 0.02 to 0.62; one study; N = 64) (Analysis 10.1).

Core body temperature (°C) of the infant taken one hour after admission (Outcome 10.2)

One study reported this outcome in terms of core body temperature in °C (axillary) one hour after admission to the NICU (Talakoub 2015).

Outcome 10.2.1: For infants at ≥ 28 and ≤ 32 weeks' gestation, data show a statistically significant difference in core body temperature one hour after admission to the NICU favouring the intervention (plastic bag + plastic hat) group when compared with the group that received plastic bag + cotton hat immediately after birth in the delivery room (MD 0.37°C, 95% CI 0.03 to 0.71; one study; N = 64) (Analysis 10.2).

Core body temperature (°C) of the infant taken two hours after admission (Outcome 10.3)

One study reported this outcome in terms of core body temperature in °C (axillary) two hours after admission to the NICU (Talakoub 2015).

Outcome 10.3.1: For infants at ≥ 28 and ≤ 32 weeks' gestation, data show a statistically significant difference in core body temperature two hours after admission to the NICU favouring the intervention (plastic bag + plastic hat) group when compared with the group that received plastic bag + cotton hat immediately after birth in the delivery room (MD 0.37°C, 95% CI 0.11 to 0.63; one study; N = 64) (Analysis 10.3).

Core body temperature (°C) on admission to the NICU or up to two hours after birth (Outcome 11.1)

One study reported this outcome in terms of core body temperature in °C (axillary) on admission to the NICU (Roberts 1981).

Outcome 11.1.1: Overall, for infants at ≥ 32 and ≤ 36 weeks' gestation (birth weight range 1360 to 2965 grams), data show no statistically significant difference between the two interventions (stockinette cap and routine care) for core body temperature on admission to the NICU (MD 0.10°C, 95% CI ‐0.21 to 0.41; one study; N = 40) (Analysis 11.1).

Outcome 11.1.2: For infants of birth weight < 2000 grams, data show a borderline statistically significant difference in core body temperature on admission to the NICU favouring the intervention (stockinette cap) group when compared with the group that received routine care immediately after birth in the delivery room (MD 0.70°C, 95% CI ‐0.01 to 1.41; one study; N = 10) (Analysis 11.1).

Outcome 11.1.3: For infants of birth weight ≥ 2000 grams, data show no statistically significant difference between the two interventions (stockinette cap and routine care) for core body temperature on admission to the NICU (MD 0.00°C, 95% CI ‐0.37 to 0.37; one study; N = 30) (Analysis 11.1).

The test for homogeneity passed with an I² value of 32.7% (low heterogeneity) for subgroup differences.

Hypothermia on admission to the NICU (core body temperature < 36.5°C, or skin temperature < 36°C) (Outcome 11.2)

Roberts 1981, in addition to reporting core body temperature on admission to the NICU as a continuous variable, provided data in a dichotomous format in terms of incidence of hypothermia in the intervention and control groups (stockinette cap and routine care). Investigators defined hypothermia as a core body temperature (axillary) < 36°C on admission to the NICU.

Outcome 11.2.1: For infants at ≥ 32 and ≤ 36 weeks' gestation (birth weight range 1360 to 2965 grams), data show no significant difference in risk of hypothermia between infants who received stockinette cap and those given routine care (RR 0.90, 95% CI 0.48 to 1.71; RD ‐0.05, 95% CI ‐0.36 to 0.26; one study; N = 40) (Analysis 11.2).

Hypothermia (skin temperature < 35.5°C for two consecutive recordings) (Outcome 12.1)

One study reported this outcome in terms of incidence of skin temperature remaining below 35.5°C for two consecutive readings (five‐minute intervals for the first hour, thereafter 15‐minute intervals during the six‐hour observation period) in the intervention and control groups (skin‐to‐skin care and routine care) (Bergman 2004). This was not a prespecified outcome at the review protocol stage.

Outcome 12.1.1: For infants of birth weight ≥ 1200 and ≤ 2199 grams, skin‐to‐skin contact significantly reduced risk of hypothermia within six hours of birth (RR 0.09, 95% CI 0.01 to 0.64; RD ‐0.56, 95% CI ‐0.84 to ‐0.27; one study; N = 31). Two infants would have to receive skin‐to‐skin contact to prevent one infant from becoming hypothermic (NNTB 2, 95% CI 1 to 4) (Analysis 12.1).

Hypoglycaemia (blood glucose < 2.6 mmol/L) (Outcome 12.2)

One study reported this outcome in terms of incidence of confirmed laboratory estimation of blood glucose < 2.6 mmol/L within the six‐hour observation period (when blood glucose was measured by heel prick at one, three, and six hours) in the intervention and control groups (skin‐to‐skin care and routine care) (Bergman 2004). This was not the prespecified definition of hypoglycaemia at the review protocol stage.

Outcome 12.2.1: For infants of birth weight ≥ 1200 and ≤ 2199 grams, data show no significant difference in risk of hypoglycaemia between infants who received skin‐to‐skin contact and those given conventional incubator care (RR 0.24, 95% CI 0.03 to 2.06; RD ‐0.18, 95% CI ‐0.43 to 0.08; one study; N = 31) (Analysis 12.2).

Core body temperature (°C) of the infant taken on admission to the NICU or up to two hours after birth (Outcome 13.1)

Two studies comprising 126 infants reported core body temperature in °C (axillary) on admission to the NICU (Brennan 1996; Chawla 2011). Each individual study showed a significant effect in favour of the intervention (thermal mattress) group for infants with birth weight ≤ 1500 grams.

Outcome 13.1.1: For infants of birth weight ≤ 1500 grams, data show a statistically significant difference in core body temperature on admission to the NICU favouring the intervention (thermal mattress) group when compared with the group that received routine care immediately after birth in the delivery room (MD 0.65°C, 95% CI 0.36 to 0.94; two studies; N = 126) (Analysis 13.1).

However, the test for homogeneity failed with an I² value of 85% (high heterogeneity). We note that this failure most likely is due to differences in methods between the two studies.

Hypothermia on admission to the NICU (core body temperature < 36.5°C, or skin temperature < 36°C) (Outcome 13.2)

Brennan 1996 and Chawla 2011, in addition to reporting core body temperature on admission to the NICU as a continuous variable, provided data in a dichotomous format in terms of incidence of hypothermia in the intervention and control groups (thermal mattress and routine care). Brennan 1996 defined hypothermia as core body temperature (axillary) < 36.5°C on admission to the NICU, and Chawla 2011 as core body temperature (axillary) < 36°C on admission to the NICU. Data for these outcome measures are presented separately.

Outcome 13.2.1: For infants of birth weight ≤ 1500 grams, the thermal mattress significantly reduced risk of hypothermia on admission to the NICU (RR 0.30, 95% CI 0.11 to 0.83; RD ‐0.58, 95% CI ‐0.91 to ‐0.26; one study; N = 24) (Analysis 13.2). Two infants would have to receive a thermal mattress to prevent one infant from becoming hypothermic (NNTB 2, 95% CI 1 to 4).

Hypothermia on admission to the NICU (core body temperature < 36.0°C) (Outcome 13.3)

Chawla 2011 also reported hypothermia as a core body temperature (axillary) < 36°C on admission to the NICU. Brennan 1996 presented individual core body temperatures as continuous outcomes so data were derived for moderate hypothermia as defined in the Chawla 2011 study. Therefore, two studies comprising 126 infants reported hypothermia as core body temperature (axillary) < 36°C on admission to the NICU (Brennan 1996; Chawla 2011). Each individual study showed a significant effect in favour of the intervention (thermal mattress) group for infants with birth weight ≤ 1500 grams.

Outcome 13.3.1: For infants of birth weight ≤ 1500 grams, a thermal mattress significantly reduced risk of hypothermia (core body temperature (axillary) < 36°C) on admission to the NICU (typical RR 0.49, 95% CI 0.32 to 0.76; typical RD ‐0.30, 95% CI ‐0.46 to ‐0.14; two studies; N = 126) (Analysis 13.3). Three infants would have to receive a thermal mattress to prevent one infant from becoming hypothermic (NNTB 3, 95% CI 2 to 7).

However, the test for homogeneity failed with an I² value of 62% (moderate heterogeneity) for RR, and 73% (moderate heterogeneity) for RD . We note that this failure is most likely due to differences in methods between the two studies. Chawla 2011 used additional thermal care measures (plastic bag without drying below the neck) for infants at < 28 weeks' gestation, which was considered to be part of routine thermal care practices. Brennan 1996, the earlier study, did not employ such additional thermal care measures.

Hypothermia on admission to the NICU (core body temperature < 35.0°C) (Outcome 13.4)

Chawla 2011 also reported hypothermia as a core body temperature (axillary) < 35°C on admission to the NICU. Brennan 1996 presented individual core body temperatures as continuous outcomes; therefore we derived data for moderate hypothermia as defined by Chawla 2011. Two studies comprising 126 infants reported hypothermia as core body temperature (axillary) < 35°C on admission to the NICU (Brennan 1996; Chawla 2011). Each individual study showed no significant difference in effect for thermal mattress and routine care for infants of birth weight ≤ 1500 grams.

Outcome 13.4.1: For infants of birth weight ≤ 1500 grams, a thermal mattress significantly reduced risk of hypothermia (core body temperature (axillary ) < 35°C) on admission to the NICU (typical RR 0.18, 95% CI 0.05 to 0.65; typical RD ‐0.18, 95% CI ‐0.29 to ‐0.07; two studies; N = 126) (Analysis 13.4). Six infants would have to receive a thermal mattress to prevent one infant from becoming hypothermic (NNTB 6, 95% CI 4 to 14).

However, the test for homogeneity failed with an I² value of 0% for RR but 84% for RD (high heterogeneity). We note that this failure most likely is due to differences in methods between the two studies. Chawla 2011 used additional thermal care measures (plastic bag without drying below the neck) for infants at < 28 weeks' gestation, which was considered to be part of routine thermal care practices. Brennan 1996, the earlier study, did not employ such additional thermal care measures.

Outside the normothermic range on admission to the NICU or up to two hours after birth (Outcome 13.5)

We derived this outcome for one study in terms of incidence of core body temperature (axillary) outside the normothermic range in intervention and control groups (thermal mattress and routine care) on admission to the NICU (Brennan 1996). Investigators defined normothermia as core body temperature (axillary) within the range 36.5°C to 37.5°C. We were unable to derive this information from Chawla 2011 because investigators defined hypothermia as core body temperature (axillary) < 36°C on admission to the NICU. The was not a prespecified outcome at the review protocol stage.

Outcome 13.5.1: For infants of birth weight ≤ 1500 grams, a thermal mattress significantly reduced risk of being outside the normothermic range (core body temperature (axillary) 36.5°C to 37.5°C) on admission to the NICU (RR 0.30, 95% CI 0.11 to 0.83; RD ‐0.58, 95% CI ‐0.91 to ‐0.26; one study; N = 24) (Analysis 13.5). Two infants would have to receive a thermal mattress to prevent one infant from being outside the normothermic range (NNTB 2, 95% CI 1 to 4).

Hyperthermia on admission to the NICU (core body temperature > 37.5°C) (Outcome 13.6)

Two studies comprising 126 infants reported this outcome in terms of incidence of hyperthermia in intervention and control groups (thermal mattress and routine care) (Brennan 1996; Chawla 2011). Chawla 2011 defined hyperthermia as core body temperature (axillary) > 37.5°C on admission to the NICU. Brennan 1996 presented individual core body temperatures as continuous outcomes, so we derived data for hyperthermia as defined by Chawla 2011. Individual data from Brennan 1996 show no infants in the thermal mattress group or in the routine care group had a core body temperature (axillary) > 37.5°C on admission to the NICU. Each individual study showed no significant difference in effect for thermal mattress and routine care among infants with birth weight ≤ 1500 grams.

Outcome 13.6.1: For infants of birth weight ≤ 1500 grams, data show no statistically significant difference in risk of hyperthermia (core body temperature (axillary) > 37.5°C) on admission to the NICU between infants who received a thermal mattress and those given routine care (RR 4.63, 95% CI 0.23 to 94.10; RD 0.03, 95% CI ‐0.03 to 0.09; two studies; N = 126) (Analysis 13.6).

The test for homogeneity passed with an I² value of 0% for RD.

Mortality (Outcome 13.7)

One study reported this outcome in terms of incidence of mortality in the intervention and control groups (thermal mattress and routine care) (Chawla 2011). Investigators did not provide a clear definition of the time frame for this outcome measure.

Outcome 13.7.1: For infants at < 32 weeks' gestation, data show no statistically significant difference in risk of mortality between infants who received a thermal mattress and those given routine care (RR 0.31, 95% CI 0.01 to 7.40; RD ‐0.02, 95% CI ‐0.07 to 0.03; one study; N = 102) (Analysis 13.7).

Major brain injury (intraventricular haemorrhage (IVH)) (Outcome 13.8)

One study reported this outcome in terms of incidence of IVH (grade Ⅲ or Ⅳ) and of cystic periventricular leukomalacia on head ultrasonography in intervention and control groups (thermal mattress and routine care) (Chawla 2011). These data are presented as two separate outcomes.

Outcome 13.8.1: For infants at < 32 weeks' gestation, data show no statistically significant difference in risk of IVH (grade Ⅲ or Ⅳ) between infants who received a thermal mattress and those given routine care (RR 4.62, 95% CI 0.56 to 38.19; RD 0.07, 95% CI ‐0.01 to 0.16; one study; N = 102) (Analysis 13.8).

Major brain injury (cystic periventricular leukomalacia) (Outcome 13.9)

One study reported this outcome in terms of the incidence of IVH (grade Ⅲ or Ⅳ) and as cystic periventricular leukomalacia on head ultrasonography in intervention and control groups (thermal mattress and routine care) (Chawla 2011). These data are presented as two separate outcomes.

Outcome 13.9.1: For infants at < 32 weeks' gestation, data show no statistically significant difference in risk of cystic periventricular leukomalacia between infants who received a thermal mattress and those given routine care (RR 1.39, 95% CI 0.24 to 7.95; RD 0.02, 95% CI ‐0.07 to 0.10; one study; N = 102) (Analysis 13.9).

Bronchopulmonary dysplasia (BPD) (Outcome 13.10)

One study reported this outcome in terms of incidence of the requirement for oxygen supplementation at 36 weeks' postmenstrual age in intervention and control groups (thermal mattress and routine care) (Chawla 2011). The was not a prespecified outcome at the review protocol stage.

Outcome 13.10.1: For infants at < 32 weeks' gestation, data show no statistically significant difference in risk of BPD between infants who received a thermal mattress and those given routine care (RR 1.34, 95% CI 0.69 to 2.61; RD 0.08, 95% CI ‐0.09 to 0.25; one study; N = 102) (Analysis 13.10).

Duration of hospital stay (days) (Outcome 13.11)

One study reported this outcome in terms of duration of hospital stay (Chawla 2011).

Outcome 13.11.1: For infants at < 32 weeks' gestation, data show no statistically significant differences between interventions (thermal mattress vs routine care) for duration of stay in hospital (MD ‐5.00 days, 95% CI ‐17.27 to 7.27; one study; N = 102) (Analysis 13.11).

Duration of ventilation (days) (Outcome 13.12)

One study reported this outcome in terms of duration of ventilation (Chawla 2011).

Outcome 13.12.1: For infants at < 32 weeks' gestation, data show no statistically significant differences between interventions (thermal mattress vs routine care) for duration of ventilation (MD ‐4.00 days, 95% CI ‐12.67 to 4.67; one study; N = 102) (Analysis 13.12).

Duration of oxygen requirement (days) (Outcome 13.13)

One study reported this outcome in terms of duration of oxygen requirement (Chawla 2011). This was not a prespecified outcome at the review protocol stage.

Outcome 13.13.1: For infants at < 32 weeks' gestation, data show no statistically significant differences between interventions (thermal mattress vs routine care) for duration of oxygen requirement (MD ‐7.00 days, 95% CI ‐19.66 to 5.66; one study; N = 102) (Analysis 13.13).

Hypoglycaemia (initial blood glucose < 40 mg/dL or < 2.2 mmol/L) (Outcome 13.14)

One study reported this outcome in terms of incidence of initial blood glucose < 40 mg/dL or < 2.2 mmol/L in intervention and control groups (thermal mattress and routine care) (Chawla 2011). This was not the prespecified definition of hypoglycaemia at the review protocol stage.

Outcome 13.14.1: For infants at < 32 weeks' gestation, data show no statistically significant differences in risk of hypoglycaemia between infants who received a thermal mattress and those given routine care (RR 1.02, 95% CI 0.47 to 2.18; RD 0.00, 95% CI ‐0.15 to 0.16; one study; N = 102) (Analysis 13.14).

Metabolic acidosis (Outcome 13.15)

One study reported this outcome in terms of incidence of pH < 7.15 with base excess ≥ 10 mmol/L on initial blood gas in intervention and control groups (thermal mattress and routine care) (Chawla 2011).

Outcome 13.15.1: For infants at < 32 weeks' gestation, data show no statistically significant differences in risk of metabolic acidosis between infants who received a thermal mattress and those given routine care (RR 0.31, 95% CI 0.03 to 2.86; RD ‐0.04, 95% CI ‐0.12 to 0.03; one study; n = 102) (Analysis 13.15).

Necrotising enterocolitis (NEC) (Outcome 13.16)

One study reported this outcome in terms of incidence of NEC > stage 2 as defined by Bell's staging in intervention and control groups (thermal mattress and routine care) (Bell 1978; Chawla 2011).

Outcome 13.16.1: For infants at < 32 weeks' gestation, data show no statistically significant differences in risk of NEC > stage 2 between infants who received a thermal mattress and those given routine care (RR 0.64, 95% CI 0.33 to 1.23; RD ‐0.12, 95% CI ‐0.29 to 0.05; one study; N = 102) (Analysis 13.16).

Sepsis (Outcome 13.17)

One study reported this outcome in terms of incidence of positive culture from sterile site such as blood or spinal fluid and intention to treat with antibiotics for seven days or longer in the intervention and control groups (thermal mattress and routine care) (Chawla 2011). This was not a prespecified outcome at the review protocol stage.

Outcome 13.17.1: For infants at < 32 weeks' gestation, data show no statistically significant differences in risk of sepsis between infants who received a thermal mattress and those given routine care (RR 0.92, 95% CI 0.48 to 1.79; RD ‐0.02, 95% CI ‐0.19 to 0.15; one study; N = 102) (Analysis 13.17).

Core body temperature (°C) of the infant taken on admission to the NICU or up to two hours after birth (Outcome 14.1)

Two studies comprising 77 infants reported this outcome in terms of core body temperature in °C (axillary) on admission to the NICU (Mathew 2012; Simon 2011). Each individual study showed no significant difference in effect for the thermal mattress versus plastic wrap or bag for infants at ≤ 28 weeks' gestation. However, Mathew 2012 is tending towards favouring plastic bag, and Simon 2011 is showing borderline significance favouring thermal mattress.

Outcome 14.1.1. For infants at ≤ 28 weeks' gestation, data show no statistically significant differences between interventions (thermal mattress and plastic bag or wrap) for core body temperature in °C on admission to the NICU (MD 0.18°C, 95% CI ‐0.18 to 0.54; two studies; N = 77) (Analysis 14.1).

The test for homogeneity failed with an I² value of 68% (moderate heterogeneity). The most plausible reason for this heterogeneity may be variability of use between practitioners when the intervention was polyethylene wrap as opposed to thermal mattress, as in Simon 2011; in some cases, displacement of the wrap could have resulted in heat loss, meaning that performance bias cannot be ruled out.

Hypothermia on admission to the NICU (core body temperature < 36.5°C, or skin temperature < 36°C) (Outcome 14.2)

Simon 2011, in addition to reporting core body temperature on admission to the NICU as a continuous variable, provided data in a dichotomous format in terms of incidence of hypothermia in intervention and comparison groups (thermal mattress and plastic wrap or bag). Investigators defined hypothermia as a core body temperature (axillary) < 36.5°C on admission to the NICU.

Outcome 14.2.1: For infants at ≥ 24 and ≤ 28 weeks' gestation with birth weight ≤ 1250 grams, data show no significant differences in risk of hypothermia between infants who received thermal mattress and those given plastic wrap (RR 0.60, 95% CI 0.32 to 1.15; RD ‐0.27, 95% CI ‐0.59 to 0.04; one study; N = 36) (Analysis 14.2).

Outside the normothermic range on admission to the NICU or up to two hours after birth (Outcome 14.3)

We were able to derive data for the normothermic range from the definitions of hypothermia (core body temperature (axillary) < 36.5°C) and hyperthermia (core body temperature (axillary) > 37.5°C) on admission to the NICU provided in Simon 2011. Investigators defined normothermic range as core body temperature (axillary) 36.5°C to 37.5°C on admission to the NICU. They reported this outcome as the incidence of core body temperature outside the normothermic range on admission to the NICU in both intervention and comparison groups (thermal mattress and plastic wrap). This was not a prespecified outcome at the review protocol stage.

Outcome 14.3.1: For infants at ≥ 24 and ≤ 28 weeks' gestation with birth weight ≤ 1250 grams, data show no significant differences in risk of being outside the normothermic range (core body temperature (axillary) 36.5°C to 37.5°C) on admission to the NICU between infants who received thermal mattress and those given plastic wrap (RR 0.69, 95% CI 0.38 to 1.24; RD ‐0.21, 95% CI ‐0.53 to 0.10; one study; N = 36) (Analysis 14.3).

Hyperthermia on admission to the NICU (core body temperature > 37.5°C) (Outcome 14.4)

Simon 2011, in addition to reporting core body temperature on admission to the NICU as a continuous variable, provided data in a dichotomous format in terms of incidence of hyperthermia in intervention and comparison groups (thermal mattress and plastic wrap). Investigators defined hyperthermia as a core body temperature (axillary) > 37.5°C on admission to the NICU.

Outcome 14.4.1: For infants at ≥ 24 and ≤ 28 weeks' gestation with birth weight ≤ 1250 grams, data show no significant differences in risk of hyperthermia between infants who received thermal mattress and those given plastic wrap (RR 3.33, 95% CI 0.14 to 76.75; RD 0.06, 95% CI ‐0.09 to 0.20; one study; N = 36) (Analysis 14.4).

Brain injury

Two studies comprising 77 infants reported this outcome in terms of incidence of grade I or II IVH ‐ in Simon 2011 ‐ and grade Ⅲ or Ⅳ IVH ‐ in Mathew 2012 and Simon 2011 ‐ among intervention and comparison groups (thermal mattress and plastic wrap or bag). These data are presented separately. For the outcome incidence of grade III or IV IVH, each individual study showed no significant differences in effect for thermal mattress versus plastic wrap or bag for infants at ≤ 28 weeks' gestation.

Brain injury (IVH grade Ⅰ or Ⅱ) (Outcome 14.5)

Outcome 14.5.1: For infants at ≥ 24 and ≤ 28 weeks' gestation with birth weight ≤ 1250 grams, data show no significant differences in risk of IVH (grade Ⅰ or Ⅱ) between infants who received thermal mattress and those given plastic wrap (RR 0.45, 95% CI 0.10 to 2.01; RD ‐0.15, 95% CI ‐0.40 to 0.10; one study; n = 36) (Analysis 14.5).

Major brain injury (IVH grade Ⅲ or Ⅳ) (Outcome 14.6)

Outcome 14.6.1: For infants at ≤ 28 weeks' gestation, data show no significant differences in risk of IVH (grade Ⅲ or Ⅳ) between infants who received thermal mattress and those given plastic wrap or bag (typical RR 0.91, 95% CI 0.31 to 2.71; typical RD ‐0.01, 95% CI ‐0.17 to 0.14; two studies; N = 77) (Analysis 14.6). The test for homogeneity passed with an I² value of 20% for RR and 19% for RD.

Mortality (death before discharge) (Outcome 14.7)

Two studies comprising 77 infants reported this outcome in terms of incidence of death before hospital discharge among intervention and comparison groups (thermal mattress and plastic wrap or bag) (Mathew 2012; Simon 2011). Each individual study showed no significant differences in effect for thermal mattress versus plastic wrap or bag for infants at ≤ 28 weeks' gestation.

Outcome 14.7.1: For infants at ≤ 28 weeks' gestation, data show no significant differences in risk of death before discharge between infants who received thermal mattress and those given plastic wrap or bag (typical RR 1.10, 95% CI 0.39 to 3.17; typical RD 0.01, 95% CI ‐0.14 to 0.16; two studies; N = 77) (Analysis 14.7). The test for homogeneity passed with an I² value of 0% for RR and RD.

Bronchopulmonary dysplasia (BPD) (Outcome 14.8)

One study reported this outcome in terms of incidence of BPD among intervention and comparison groups (thermal mattress and plastic wrap) (Simon 2011). Investigators did not provide a clear definition of BPD. This was not a prespecified outcome at the review protocol stage.

Outcome 14.8.1: For infants at ≥ 24 and ≤ 28 weeks' gestation with birth weight ≤ 1250 grams, data show no significant differences in risk of BPD before discharge between infants who received thermal mattress and those given plastic wrap (RR 0.75, 95% CI 0.40 to 1.37; RD ‐0.16, 95% CI ‐0.48 to 0.16; one study; N = 36) (Analysis 14.8).

Hypotension (Outcome 14.9)

One study reported this outcome in terms of mean blood pressure less than gestational age in weeks during the first 24 hours of life and received treatment with fluid bolus, pressors, or both in intervention and active comparison groups (thermal mattress and plastic bag) (Mathew 2012).

Outcome 14.9.1: For infants at ≤ 28 weeks' gestation, data show no significant differences in risk of hypotension in the first 24 hours of life between infants who received thermal mattress and those given plastic bag (RR 1.50, 95% CI 0.71 to 3.17; RD 0.17, 95% CI ‐0.13 to 0.46; one study; N = 41) (Analysis 14.9).

Necrotising enterocolitis (NEC) (Outcome 14.10)

Two studies comprising 77 infants reported this outcome in terms of incidence of NEC among intervention and comparison groups (thermal mattress and plastic wrap or bag) (Mathew 2012; Simon 2011). Investigators provided no clear definitions. Each individual study showed no significant differences in effect for thermal mattress and plastic wrap or bag.

Outcome 14.10.1: For infants at ≤ 28 weeks' gestation, data show no significant differences in risk of NEC between infants who received thermal mattress and those given plastic wrap or bag (typical RR 1.92, 95% CI 0.61 to 5.97; typical RD 0.09, 95% CI ‐0.06 to 0.25; two studies; N = 77) (Analysis 14.10). The test for homogeneity passed with an I² value of 0% for RR and RD.

Patent ductus arteriosus

One study reported this outcome in terms of overall incidence of PDA among those treated with medication only and those treated with ligation in the intervention and comparison groups (thermal mattress and plastic wrap) (Simon 2011).

Overall patent ductus arteriosus (PDA) (Outcome 14.11)

Outcome 14.11.1: For infants at ≥ 24 and ≤ 28 weeks' gestation with birth weight ≤ 1250 grams, data show no significant differences in risk of PDA between infants who received thermal mattress and those given plastic wrap (RR 1.76, 95% CI 0.88 to 3.49; RD 0.28, 95% CI ‐0.04 to 0.59; one study; N = 36) (Analysis 14.11).

Patent ductus arteriosus (PDA) treated with medication only (Outcome 14.12)

Outcome 14.12.1: For infants at ≥ 24 and ≤ 28 weeks' gestation with birth weight ≤ 1250 grams, data show no significant differences in risk of PDA treated with medication only between infants who received thermal mattress and those given plastic wrap (RR 1.44, 95% CI 0.69 to 3.01; RD 0.16, 95% CI ‐0.16 to 0.48; one study; N = 36) (Analysis 14.12).

Patent ductus arteriosus (PDA) treated with ligation (Outcome 14.13)

Outcome 14.13.1: For infants at ≥ 24 and ≤ 28 weeks' gestation with birth weight ≤ 1250 grams, data show no significant differences in risk of PDA with ligation treatment between infants who received thermal mattress and those given plastic wrap (RR 5.56, 95% CI 0.29 to 108.16; RD 0.12, 95% CI ‐0.06 to 0.29; one study; N = 36) (Analysis 14.13).

Retinopathy of prematurity (ROP)

Simon 2011 reported this outcome in terms of overall incidence of ROP (all grades); Mathew 2012 reported incidence of ROP with laser therapy among intervention and comparison groups (thermal mattress and plastic wrap or bag). This was not a prespecified outcome at the review protocol stage.

Retinopathy of prematurity (ROP) all grades (Outcome 14.14)

Outcome 14.14.1: For infants at ≥ 24 and ≤ 28 weeks' gestation with birth weight ≤ 1250 grams, data show no significant differences in risk of ROP (all grades) between infants who received thermal mattress and those given plastic wrap (RR 0.48, 95% CI 0.15 to 1.56; RD ‐0.19, 95% CI ‐0.47 to 0.09; one study; N = 36) (Analysis 14.14).

Retinopathy of prematurity (ROP) treated with laser therapy (Outcome 14.15)

Outcome 14.15.1: For infants at ≤ 28 weeks' gestation, data show no significant differences in risk of ROP with laser therapy between infants who received thermal mattress and those given plastic bag (RR 0.53, 95% CI 0.05 to 5.35; RD ‐0.05, 95% CI ‐0.20 to 0.11; one study; N = 41) (Analysis 14.15).

Spontaneous intestinal perforation (SIP) (Outcome 14.16)

One study reported this outcome in terms of incidence of SIP among intervention and comparison groups (thermal mattress and plastic bag) (Mathew 2012). Investigators provided no clear definition. This was not a prespecified outcome at the review protocol stage.

Outcome 14.16.1: For infants at ≤ 28 weeks' gestation, data show no significant differences in risk of SIP between infants who received thermal mattress and those given plastic bag (RR 0.53, 95% CI 0.11 to 2.56; RD ‐0.09, 95% CI ‐0.30 to 0.12; one study; N = 41) (Analysis 14.16).

Worst base deficit in first 24 hours of life (Outcome 14.17)

One study reported this outcome in terms of lowest pH and highest base deficit in the first 24 hours after birth (Mathew 2012).

Outcome 14.17.1: For infants at ≤ 28 weeks' gestation, data show no statistically significant differences between interventions (thermal mattress and plastic bag) for worst base deficit in the first 24 hours after birth (MD ‐1.70 mEq/L, 95% CI ‐3.99 to 0.59; one study; N = 41) (Analysis 14.17).

Worst pH in first 24 hours of life (Outcome 14.18)

One study reported this outcome in terms of worst pH in the first 24 hours after birth (Mathew 2012). This was not a prespecified outcome at the review protocol stage.

Outcome 14.18.1: For infants at ≤ 28 weeks' gestation, data show a statistically significant difference in worst pH in the first 24 hours after birth favouring the thermal mattress group when compared with the plastic bag group with intervention provided immediately after birth in the delivery room (MD ‐0.09, 95% CI ‐0.13 to ‐0.05; one study; N = 41) (Analysis 14.18).

Core body temperature (°C) of the infant taken on admission to the NICU or up to two hours after birth (Outcome 15.1)

Two studies comprising 119 infants reported this outcome in terms of core body temperature in °C on admission to the NICU in intervention and active comparator groups (plastic bag + thermal mattress and plastic bag only) (Leslie 2007; McCarthy 2013). Data show core body temperature in °C rectal ‐ for McCarthy 2013 ‐ and axillary ‐ for Leslie 2007. Overall, Leslie 2007 showed no significant differences in effect for plastic bag + thermal mattress and plastic bag only for infants at < 29 weeks' gestation, whereas McCarthy 2013 showed a significant effect in favour of the plastic bag + mattress intervention for infants at < 31 weeks' gestation and for the subgroup at < 28 weeks' gestation.

Outcome 15.1.1: Overall, for infants at < 31 weeks' gestation, data show a statistically significant difference for core body temperature on admission to the NICU favouring the plastic bag + thermal mattress intervention when compared with plastic bag only immediately after birth in the delivery room (MD 0.37°C, 95% CI 0.09 to 0.66; two studies; N = 119) (Analysis 15.1).

The overall test for homogeneity passed with an I² value of 0% and for subgroup differences with an I² value of 19.3%.

Outcome 15.1.2: For infants at < 28 weeks' gestation, data show a statistically significant difference for core body temperature on admission to the NICU favouring the plastic bag + thermal mattress intervention when compared with plastic bag only immediately after birth in the delivery room (MD 0.57°C, 95% CI 0.20 to 0.94; two studies; N = 76) (Analysis 15.1). The test for homogeneity passed with an I² value of 43% (low heterogeneity).

Outcome 15.1.3: For infants at 28 to 30 weeks' gestation, data show no statistically significant differences between interventions (plastic bag + thermal mattress and plastic bag only) for core body temperature on admission to the NICU (MD 0.10°C, 95% CI ‐0.36 to 0.56; one study; N = 43) (Analysis 15.1).

Hypothermia on admission to the NICU (core body temperature < 36.5°C, or skin temperature < 36°C) (Outcome 15.2)

Leslie 2007 and McCarthy 2013, in addition to reporting core body temperature on admission to the NICU as a continuous variable, provided data in a dichotomous format in terms of incidence of hypothermia seen as core body temperature (rectal) < 36.5°C ‐ in McCarthy 2013 ‐ and hypothermia seen as core body temperature (axillary) < 36.5°C ‐ in Leslie 2007 ‐ in the intervention and comparison groups (plastic bag + thermal mattress and plastic bag only). Each individual study showed no significant differences in effect for plastic bag + thermal mattress and plastic bag only.

Outcome 15.2.1: Overall, for infants at < 31 weeks' gestation, data show no significant differences in risk of hypothermia between infants who received plastic bag + thermal mattress and those given plastic bag only (typical RR 0.93, 95% CI 0.45 to 1.90; typical RD ‐0.01, 95% CI ‐0.15 to 0.12; two studies; N = 119) (Analysis 15.2). The overall test for homogeneity failed with an I² value of 55% (moderate heterogeneity) for RR and 65% (moderate heterogeneity) for RD, but passed for subgroup differences with an I² value of 16.8% for RR and 37% (low heterogeneity) for RD.

Outcome 15.2.2: For infants at < 28 weeks' gestation, data show no significant differences in risk of hypothermia between infants who received plastic bag + thermal mattress and those given plastic bag only (typical RR 0.66, 95% CI 0.29 to 1.46; typical RD ‐0.10, 95% CI ‐0.28 to 0.08; two studies; N = 76) (Analysis 15.2). The overall test for homogeneity passed with an I² value of 0% for RR and 14% for RD.

Outcome 15.2.3: For infants at 28 to 30 weeks' gestation, data show no significant differences in risk of hypothermia between infants who received plastic bag + thermal mattress and those given plastic bag only (RR 3.82, 95% CI 0.46 to 31.43; RD 0.13, 95% CI ‐0.05 to 0.32; one study; N = 43) (Analysis 15.2).

Outside the normothermic range on admission to the NICU or up to two hours after birth (Outcome 15.3)

McCarthy 2013, in addition to reporting core body temperature on admission to the NICU as a continuous variable, provided data in a dichotomous format in terms of incidence of normothermia (core body temperature (rectal) 36.5°C to 37.5°C) in intervention and comparison groups (plastic bag + thermal mattress and plastic bag only). Leslie 2007 provided data for incidence of hypothermia and hyperthermia; therefore for the purposes of meta‐analysis, we defined normothermia as core body temperature (axillary) 36.5°C to 38°C. We meta‐analysed the incidence of core body temperature outside the defined normothermic range. Overall, Leslie 2007 showed no significant differences in effect for plastic bag + thermal mattress and plastic bag only among infants at < 29 weeks' gestation, whereas McCarthy 2013 showed a significant effect in favour of the comparator (plastic bag only) for infants at < 31 weeks' gestation, and for the subgroup at < 28 weeks' gestation. This was not a prespecified outcome at the review protocol stage.

Outcome 15.3.1: Overall, for infants at < 31 weeks' gestation, data show no significant differences in the risk of being outside the normothermic range between those who received plastic bag + thermal mattress and those given plastic bag only (typical RR 1.46, 95% CI 0.94 to 2.27; typical RD 0.16, 95% CI ‐0.00 to 0.33; two studies; N = 119) (Analysis 15.3). The overall test for homogeneity failed with an I² value of 87% (high heterogeneity) for RR and 88% (high heterogeneity) for RD, but passed for subgroup differences with an I² value of 0% for RR and for RD.

Outcome 15.3.2: For infants at < 28 weeks' gestation, data show no significant differences in the risk of being outside the normothermic range between infants who received plastic bag + thermal mattress and those given plastic bag only (typical RR 1.23, 95% CI 0.69 to 2.18; typical RD 0.08, 95% CI ‐0.12 to 0.29; two studies; N = 76) (Analysis 15.4). The test for homogeneity failed with an I² value of 83% (high heterogeneity) for RR and 89% (high heterogeneity) for RD.

Outcome 15.3.3: For infants at 28 to 30 weeks' gestation, data show no significant differences (borderline) in risk of being outside the normothermic range between infants who received plastic bag + thermal mattress and those given plastic bag only (RR 1.91, 95% CI 0.96 to 3.78; RD 0.30, 95% CI 0.02 to 0.59; one study; N = 43) (Analysis 15.3).

Hyperthermia on admission to the NICU (core body temperature > 37.5°C) (Outcome 15.4)

Leslie 2007 and McCarthy 2013, in addition to reporting core body temperature on admission to the NICU as a continuous variable, provided data in a dichotomous format in terms of incidence of hyperthermia defined as core body temperature (rectal) > 37.5°C by McCarthy 2013, and as core body temperature (axillary) > 38°C by Leslie 2007, among intervention and comparison groups (plastic bag + thermal mattress and plastic bag only). Overall, Leslie 2007 showed no significant differences in effect for plastic bag + thermal mattress and plastic bag only among infants at < 29 weeks' gestation, whereas McCarthy 2013 showed a significant effect in favour of the comparator (plastic bag only) for infants at < 31 weeks' gestation.

Outcome 15.4.1: Overall, for infants at < 31 weeks' gestation, plastic bag + thermal mattress significantly increased risk of hyperthermia on admission to the NICU when compared with plastic bag only (typical RR 2.15, 95% CI 1.07 to 4.32; typical RD 0.18, 95% CI 0.03 to 0.32; two studies; N = 119) (Analysis 15.4). For every six infants receiving plastic bag and thermal mattress, one infant would be hyperthermic on admission to the NICU (NNTH 6, 95% CI 3 to 33). The overall test for homogeneity passed for RR with an I² value of 16%, and for subgroup differences with an I² value of 0% for both RR and RD, but failed for RD with an I² value of 76% (moderate heterogeneity). This may be attributable to differences in the definition of hyperthermia, which requires a higher temperature in Leslie 2007 (> 38°C).

Outcome 15.4.2: For infants at < 28 weeks' gestation, data show no significant differences in risk of hyperthermia between infants who received plastic bag + thermal mattress and those given plastic bag only (typical RR 2.99, 95% CI 0.93 to 9.65; typical RD 0.18, 95% CI 0.02 to 0.34; two studies; N = 76) (Analysis 15.4). The test for homogeneity failed for RR with an I² value of 68% (moderate heterogeneity), and for RD with an I² value of 87% (high heterogeneity).

Note: Computational errors can occur when one or both arms of a study have a zero count. RevMan software compensates by adding 0.5 to each cell in a two‐by‐two table.

Outcome 15.4.3: For infants at 28 to 30 weeks' gestation, data show no significant differences in risk of hyperthermia between infants who received plastic bag + thermal mattress and those given plastic bag only (RR 1.59, 95% CI 0.70 to 3.60; RD 0.17, 95% CI ‐0.12 to 0.45; one study; N = 43) (Analysis 15.4).

Major brain injury: abnormal cranial ultrasonography (Outcome 15.5)

One study reported this outcome in terms of incidence of abnormal cranial ultrasonography (IVH ≥ grade Ⅲ, periventricular leukomalacia, or post‐haemorrhagic hydrocephalus) in the intervention and comparison groups (plastic bag + thermal mattress and plastic bag only) (McCarthy 2013). This was not a prespecified outcome at the review protocol stage.

Outcome 15.5.1: For infants at < 31 weeks' gestation, data show no significant differences in risk of abnormal cranial ultrasonography between infants who received plastic bag + thermal mattress and those given plastic bag only (RR 0.32, 95% CI 0.03 to 2.89; RD ‐0.06, 95% CI ‐0.17 to 0.05; one study; N = 72).

Mortality (death within hospital stay) (Outcome 15.6)

Two studies comprising 119 infants reported this outcome in terms of incidence of death before hospital discharge in intervention and comparison groups (plastic bag + thermal mattress and plastic bag only) (Leslie 2007; McCarthy 2013). Each individual study showed no significant differences in effect for plastic bag + thermal mattress and plastic bag only among infants at < 31 weeks' gestation.

Outcome 15.6.1: For infants at < 31 weeks' gestation, data show no significant differences in risk of death before hospital discharge between infants who received plastic bag + thermal mattress and those given plastic bag only (RR 0.73, 95% CI 0.32 to 1.66; RD ‐0.05, 95% CI ‐0.18 to 0.08; two studies; N = 119). The test for homogeneity passed with an I² value of 0% for RR and RD.

Chronic lung disease (Outcome 15.7)

One study reported this outcome in terms of the incidence of requirement for oxygen supplementation on the date of 36 weeks' adjusted gestation in intervention and comparison groups (plastic bag + thermal mattress and plastic bag only) (McCarthy 2013).

Outcome 15.7.1: For infants at < 31 weeks' gestation, data show no significant differences in risk of chronic lung disease between infants who received plastic bag + thermal mattress and those given plastic bag only (RR 1.73, 95% CI 0.72 to 4.18; RD 0.13, 95% CI ‐0.07 to 0.32; one study; N = 72).

Coagulation support (Outcome 15.8)

One study reported this outcome in terms of incidence of the use of platelets or fresh frozen plasma or cryoprecipitate in intervention and comparison groups (plastic bag + thermal mattress and plastic bag only) (Leslie 2007). This was not a prespecified outcome at the review protocol stage.

Outcome 15.8.1: For infants at < 29 weeks' gestation, data show no significant differences in risk of coagulation support between infants who received plastic bag + thermal mattress and those given plastic bag only (RR 1.04, 95% CI 0.30 to 3.69; RD 0.01, 95% CI ‐0.21 to 0.22; one study; N = 47).

Inotrope use (Outcome 15.9)

Two studies comprising 119 infants reported this outcome in terms of incidence of inotrope use (dopamine or dobutamine or hydrocortisone) in intervention and comparison groups (plastic bag + thermal mattress and plastic bag only) (Leslie 2007; McCarthy 2013). This was not a prespecified outcome at the review protocol stage. Each individual study showed no significant difference in effect for the plastic bag + thermal mattress and plastic bag only among infants at < 31 weeks' gestation.

Outcome 15.9.1: For infants at < 31 weeks' gestation, data show no significant differences in risk of Inotrope use between infants who received plastic bag + thermal mattress and those given plastic bag only (RR 1.14, 95% CI 0.61 to 2.11; RD 0.03, 95% CI ‐0.12 to 0.19; two studies; N = 119). The test for homogeneity passed with an I² value of 0% for RR and RD.

Intubated during admission (Outcome 15.10)

One study reported this outcome in terms of incidence of intubation during admission in the intervention and comparison groups (plastic bag + thermal mattress and plastic bag only) (McCarthy 2013). This was not a prespecified outcome at the review protocol stage.

Outcome 15.10.1: For infants at < 31 weeks' gestation, data show no significant differences in risk of intubation during admission between infants who received plastic bag + thermal mattress and those given plastic bag only (RR 0.98, 95% CI 0.73 to 1.32; RD ‐0.01, 95% CI ‐0.22 to 0.20; one study; N = 72).

Greater than or equal to one dose of surfactant during admission (Outcome 15.11)

One study reported this outcome in terms of incidence of requirement for one or more doses of surfactant during admission in intervention and comparison groups (plastic bag + thermal mattress and plastic bag only) (McCarthy 2013). This was not a prespecified outcome at the review protocol stage.

Outcome 15.11.1: For infants at < 31 weeks' gestation, data show no significant differences in risk of receiving one or more doses of surfactant during admission between infants who received plastic bag + thermal mattress and those given plastic bag only (RR 0.99, 95% CI 0.70 to 1.38; RD ‐0.01, 95% CI ‐0.23 to 0.21; one study; N = 72).