Liang 2009.

Methods	Open randomised trial. The method of randomisation and means of allocation concealment were not described. Despite randomisation, group sizes were unequal with 38 subjects in the phenobarbital group versus 47 in the control group Blinding of intervention: no Complete follow‐up: uncertain Blinding of outcome measurement: uncertain
Participants	Preterm infants with gestational age 28‐34 weeks from a single centre were included. No birthweight or need for mechanical ventilation criteria. No information given on withdrawal or loss of subjects after enrolment
Interventions	Phenobarbital 20 mg/kg split in 2 doses 12 h apart, started within 6 h of birth. Followed 12 h later by a maintenance dose of 5 mg/kg/day for 5 days. Route of administration was not specified. Drug levels were not monitored. No use of a placebo
Outcomes	Grade of IVH (graded 1‐4 with 3 and 4 being severe) on brain CT within 1 week of age. Mortality data were given, but age at death was unclear
Notes	Randomisation resulted in unequal group sizes. The authors did not explain this. High mortality rate noted, with uncertainty about whether any subjects died prior to undergoing CT or underwent postmortem to identify IVH. No assessment of IVH prior to trial entry
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	The method of randomisation was not described
Allocation concealment (selection bias)	Unclear risk	No information provided
Blinding of participants and personnel (performance bias) All outcomes	High risk	Participants and personnel were probably not blinded for intervention
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	No description of blinding of outcome assessment
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	No information provided
Selective reporting (reporting bias)	Unclear risk	Insufficient information to make a judgement as we have no access to a trial protocol