Bagheri 2018.

Study characteristics
Methods	Single‐centre randomized controlled trial
Participants	Inclusion criteria Gestational age of < 34 weeks Exclusion criteria Pulmonary artery atresia Aortic coarctation Genetic disorders Persistent pulmonary hypertension Severe asphyxia Hepatic failure 5th minute Apgar score < 5 Cord blood pH < 7
Interventions	Active intervention (n = 80) Prophylactic IV acetaminophen, 1st dose 20 mg/kg at 12 hours, then 7.5 mg/kg every 6 hours up to <4 days old Control (n = 80) No placebo
Outcomes	Relevant outcomes for this study included Mortality
Notes	Primary study location: Kerman, Iran Study period: November 2015 to November 2016 Trial registration: IR.KMU.REC.1395.841 and IRCT2017012718994N2
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	It was not stated how randomization sequence was generated
Allocation concealment (selection bias)	Unclear risk	Allocation concealment method not specified
Blinding of participants and personnel (performance bias) All outcomes	High risk	The authors say the nurses giving injections were unaware of case‐control division as paracetamol can be used as analgesic. Following first dose of paracetamol the infants were examined closely for any new symptoms prompting exclusion or further testing. This detailed examination would not have occurred in the control group.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Cardiologists evaluating echocardiograms were blinded.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Outcome data reported for all randomized infants
Selective reporting (reporting bias)	Unclear risk	The trial was registered with Iranian Registry of Clinical Trials (IRCT2017012718994N2) in 2017 retrospectively following complete recruitment (2015‐2016). There does not seem to be any obvious protocol deviations.
Other bias	Low risk	none noted