Specialised antenatal clinics for women with a pregnancy at high risk of preterm birth (excluding multiple pregnancy) to improve maternal and infant outcomes
Abstract
This is a protocol for a Cochrane Review (Intervention). The objectives are as follows:
To assess using the best available evidence, the value of specialised antenatal clinics for women with a pregnancy at high risk of preterm delivery when compared with 'standard' antenatal clinics.
Background
Preterm birth occurs in up to 6% to 10% of all births and is associated with perinatal mortality and morbidity (Lumley 2003). Nearly half of all preterm births are due to preterm labour. Preterm birth is associated with emotional and economic costs to both the family and society (Petrou 2001). Once congenital anomalies are excluded, preterm birth is responsible for the majority of neonatal deaths and is the major cause of disability in childhood (Hack 1999). The majority of mortality and morbidity occurs with extremely preterm birth (defined as birth before 28 weeks' gestation). However, whilst the incidence of death and long‐term handicap is relatively low in those born after 32 weeks, they make up over 80% of all preterm deliveries and therefore this group of infants has a significant impact upon the burden that preterm birth makes on public health (Kramer 2000). Despite research over the past few decades, no decrease in the incidence of preterm birth has occurred, although there have been improved survival and outcomes for premature infants.
Amongst the risk factors for preterm birth, previous preterm delivery is a strong predictor and the earlier the birth the more likely it is to be repeated at the same gestation (Hoffman 1984). Other risk factors include cervical weakness, cervical trauma and stress (El‐Bastawissi 1999; Iams 2004; Ruis 2003). Specialised clinics for women with a history of spontaneous preterm delivery have been advocated, with non‐randomised cohort data suggesting improved perinatal outcomes with the provision of intensive antenatal education, continuity of carer and individualised care (Bienstock 2001). Such specialised clinics may also see women with previous preterm prelabour rupture of the membranes, previous late miscarriage (16 weeks 0 days to 23 weeks 6 days of gestation), or prior cervical surgery. Prediction of risk may utilise ultrasound assessment of cervical length and the presence of fetal fibronectin in cervico‐vaginal secretions. The package of care offered in such clinics may include promising prophylactic interventions for labour prevention including progesterone, clindamycin or cervical cerclage (Althuisius 1998; da Fonesca 2003; Ugwumadu 2003). However, stress has been associated with enhanced risk of preterm delivery and there is evidence that whilst some pregnant women welcome referral to a specialist clinic during pregnancy, others experience it as unsettling (Jackson 2006).
The aim of this review is to assess, using the best available evidence, the value of such specialised antenatal clinics for women with a pregnancy at high risk of preterm delivery when compared with 'standard' antenatal clinic attendance. The primary outcomes relate to maternal and neonatal morbidity, and maternal and perinatal mortality. In women with multiple pregnancy, who have an increased risk of premature delivery, specialised clinics have been advocated in an attempt to improve perinatal outcomes. The value of specialised antenatal care for women with a multiple pregnancy when compared with 'standard' antenatal care is the subject of a different Cochrane review (Dodd 2007).
Objectives
To assess using the best available evidence, the value of specialised antenatal clinics for women with a pregnancy at high risk of preterm delivery when compared with 'standard' antenatal clinics.
Methods
Criteria for considering studies for this review
Types of studies
All published, unpublished, and ongoing randomised controlled trials. We will also include cluster‐randomised trials. We will not include quasi‐randomised controlled trials.
Types of participants
Pregnant women with a singleton pregnancy considered by the trial authors to be at high risk of preterm labour.
Types of interventions
'Specialised' antenatal clinics (as defined by trial authors) compared with 'standard' antenatal clinic care (as defined by trial authors).
Types of outcome measures
We will include outcomes in the analysis if data are available according to original allocation and reasonable measures were taken to minimise observer bias. Only outcomes with available data will appear in the analysis tables. In order to minimise the risk of bias, we will base the conclusions solely on the prestated outcomes.
Primary outcomes
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Perinatal death (defined as stillbirth after trial entry, or death of a liveborn infant up to seven days of age)
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Extremely preterm birth (defined as birth less than 28 weeks' gestation)
Secondary outcomes
Secondary outcomes relate to pregnancy outcomes, complications, satisfaction and costs.
Pregnancy outcomes
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Development of antenatal complications (including preterm labour (actual or suspected), preterm prelabour ruptured membranes, intrauterine growth restriction (estimated fetal weight less than 10th centile for gestational age))
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Preterm birth (defined as birth before 37 weeks' gestation)
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Very preterm birth (defined as birth before 34 weeks' gestation)
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Gestation at birth
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Infection requiring intravenous antibiotics
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Mode of birth
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Postnatal depression
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Breastfeeding
Complciations for infants
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Instrumental vaginal birth
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Neonatal intensive care unit admission
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Respiratory distress syndrome
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Parameters of birth asphyxia (neonatal irritability, neonatal seizures, neonatal hypotonia, abnormal level of consciousness, neonatal apnoea, tube feeding greater than 48 hours)
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Complications of prematurity
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Disability at childhood follow up (including deafness, blindness, neurodisability or cerebral palsy)
Measures of satisfaction
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Women's satisfaction
Costs
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Costs associated with 'specialised' antenatal care versus 'standard' care
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Number of antenatal visits
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Number of antenatal admissions and length of admission
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Length of maternal postnatal stay
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Length of stay in neonatal intensive care unit
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Infant length of hospital stay
Search methods for identification of studies
Electronic searches
We will contact the Trials Search Co‐ordinator to search the Cochrane Pregnancy and Childbirth Group's Trials Register.
The Cochrane Pregnancy and Childbirth Group's Trials Register is maintained by the Trials Search Co‐ordinator and contains trials identified from:
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quarterly searches of the Cochrane Central Register of Controlled Trials (CENTRAL);
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monthly searches of MEDLINE;
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handsearches of 30 journals and the proceedings of major conferences;
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weekly current awareness search of a further 37 journals.
Details of the search strategies for CENTRAL and MEDLINE, the list of handsearched journals and conference proceedings, and the list of journals reviewed via the current awareness service can be found in the 'Search strategies for identification of studies' section within the editorial information about the Cochrane Pregnancy and Childbirth Group.
Trials identified through the searching activities described above are given a code (or codes) depending on the topic. The codes are linked to review topics. The Trials Search Co‐ordinator searches the register for each review using these codes rather than keywords.
We will not apply any language restrictions.
Data collection and analysis
Selection of studies
We will assess for inclusion all potential studies we identify as a result of the search strategy. We will resolve any disagreement through discussion or if required consult an outside person.
Data extraction and management
We will design a form to extract data. At least two review authors will extract the data using the agreed form. We will resolve discrepancies through discussion. We will use the Review Manager software (RevMan 2003) to double enter all the data or a subsample.
When information regarding any of the above is unclear, we will attempt to contact authors of the original reports to provide further details.
We will assign quality scores for concealment of allocation using the criteria described in Section six of the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2005): A = adequate; B = unclear; C = inadequate; D = not used. In addition, we will assign quality scores to each trial for completeness of follow up, as follows: (A) less than 3% of participants excluded; (B) 3% to 9.9% of participants excluded; (C) 10% to 19.9% of participants excluded; (D) 20% or more excluded; and (E) unclear. Blinding of the woman and caregivers will not be possible. It may be possible for blinding of outcome assessors. Both authors will extract data separately and will double enter the data. We will resolve any discrepancies by discussion. There will be no blinding of authorship.
Cluster randomised and individually randomised trials will be combined in the same analyses and the numbers of events and denominators will be adjusted for cluster trials, (using the methods described in the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2005). This will require an estimate of the intracluster correlation coefficient (ICC); in order of preference this will be (1) an estimate provided by the trial in question, (2) an estimate from another study of a similar population, (3) a guess ‐ in which case it will be essential to carry out a sensitivity analysis to see the effects of varying the ICC on the conclusions of the analysis.
For dichotomous data, we will calculate relative risks and 95% confidence intervals and, in the absence of heterogeneity, we will pool results using a fixed‐effect model. We will test for heterogeneity using the I² statistic. We will explore the reasons for the presence of heterogeneity. Primary analyses will be based on intention to treat. We will carry out sensitivity analyses to evaluate the effect of trial quality.
Subgroup analyses
We will conduct planned subgroup analyses classifying whole trials by interaction tests as described by Deeks 2001.
We plan to carry out the following subgroup analyses:
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parity (nulliparous versus multiparous women);
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type of care received (that is, time that specialised care commenced; number of antenatal visits; use of ultrasound);
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use of cervical length measurements (transvaginal ultrasound versus no transvaginal ultrasound).
