Appendix 1. Standard search methods

PubMed: ((infant, newborn[MeSH] OR newborn OR neonate OR neonatal OR premature OR low birth weight OR VLBW OR LBW or infan* or neonat*) AND (randomized controlled trial [pt] OR controlled clinical trial [pt] OR randomized [tiab] OR placebo [tiab] OR drug therapy [sh] OR randomly [tiab] OR trial [tiab] OR groups [tiab]) NOT (animals [mh] NOT humans [mh]))

Embase: (infant, newborn or newborn or neonate or neonatal or premature or very low birth weight or low birth weight or VLBW or LBW or Newborn or infan* or neonat*) AND (human not animal) AND (randomized controlled trial or controlled clinical trial or randomized or placebo or clinical trials as topic or randomly or trial or clinical trial)

CINAHL: (infant, newborn OR newborn OR neonate OR neonatal OR premature OR low birth weight OR VLBW OR LBW or Newborn or infan* or neonat*) AND (randomized controlled trial OR controlled clinical trial OR randomized OR placebo OR clinical trials as topic OR randomly OR trial OR PT clinical trial)

Cochrane Library: (infant or newborn or neonate or neonatal or premature or preterm or very low birth weight or low birth weight or VLBW or LBW)

Appendix 2. Risk of bias tool

We will use the standard methods of Cochrane and the Cochrane Neonatal Review Group to assess the methodological quality (to meet the validity criteria) of the trials. For each trial, we will seek information regarding the method of randomization and blinding and reporting of all outcomes of all infants enrolled in the trial. We will assess each criterion as having low, high, or unclear risk. Two review authors will separately assess each study. We will resolve disagreements by discussion. We will add this information to the "Characteristics of included studies" table. We will evaluate the following issues and will enter findings into the "Risk of bias" table.

• Sequence generation (checking for possible selection bias). Was the allocation sequence adequately generated?

For each included study, we will categorize the method used to generate the allocation sequence as:

• • low risk (any truly random process, e.g. random number table, computer random number generator);

  • high risk (any non‐random process, e.g. odd or even date of birth, hospital or clinic record number); or

  • unclear risk.

• Allocation concealment (checking for possible selection bias). Was allocation adequately concealed?

For each included study, we will categorize the method used to conceal the allocation sequence as:

• • low risk (e.g. telephone or central randomization, consecutively numbered sealed opaque envelopes);

  • high risk (open random allocation, unsealed or non‐opaque envelopes, alternation, date of birth); or

  • unclear risk.

• Blinding of participants and personnel (checking for possible performance bias). Was knowledge of the allocated intervention adequately prevented during the study?

For each included study, we will categorize the methods used to blind study participants and personnel from knowledge of which intervention a participant received. We will assess blinding separately for different outcomes or classes of outcomes. We will categorize the methods as:

• • low risk, high risk, or unclear risk for participants; and

  • low risk, high risk, or unclear risk for personnel.

• Blinding of outcome assessment (checking for possible detection bias). Was knowledge of the allocated intervention adequately prevented at the time of outcome assessment?

For each included study, we will categorize the methods used to blind outcome assessment. We will assess blinding separately for different outcomes or classes of outcomes. We will categorize the methods as:

• • low risk for outcome assessors;

  • high risk for outcome assessors; or

  • unclear risk for outcome assessors.

• Incomplete outcome data (checking for possible attrition bias through withdrawals, dropouts, protocol deviations). Were incomplete outcome data adequately addressed?

For each included study and for each outcome, we will describe the completeness of data including attrition and exclusions from the analysis. We will note whether attrition and exclusions were reported, numbers included in the analysis at each stage (compared with the total number of randomized participants), reasons for attrition or exclusion when reported, and whether missing data were balanced across groups or were related to outcomes. When trial authors reported or supplied sufficient information, we will re‐include missing data in the analyses. We will categorize the methods as:

• • low risk (< 20% missing data);

  • high risk (≥ 20% missing data); or

  • unclear risk.

• Selective reporting bias. Are reports of the study free of the suggestion of selective outcome reporting?

For each included study, we will describe how we investigated the possibility of selective outcome reporting bias and what we found. We will assess the methods as:

• • low risk (when it is clear that all of the study's prespecified outcomes and all expected outcomes of interest to the review have been reported);

  • high risk (when not all of the study's prespecified outcomes have been reported; one or more reported primary outcomes were not prespecified outcomes of interest and are reported incompletely and so cannot be used; or study fails to include results of a key outcome that would have been expected to have been reported); or

  • unclear risk.

• Other sources of bias. Was the study apparently free of other problems that could put it at high risk of bias?

For each included study, we will describe any important concerns we had about other possible sources of bias (e.g. whether a potential source of bias was related to the specific study design, whether the trial was stopped early owing to some data‐dependent process). We will assess whether each study was free of other problems that could put it at risk of bias as:

• • low risk;

  • high risk; or

  • unclear risk.

If needed, we plan to explore the impact of the level of bias by undertaking sensitivity analyses.