2. 'Risk of bias' assessment criteria for randomised controlled trials.

Selection bias Sequence generation (adequate: yes/no): if the rule for allocating interventions to participants was based on some chance (random) process. Allocation concealment (adequate: yes/no): if the randomisation method did not allow investigator and child to know or influence allocation of treatment before eligible children entered the study.

Performance bias Blinding of care providers (yes/no): if knowledge of the allocated intervention was adequately prevented during the study. Blinding of participants (yes/no): if knowledge of the allocated intervention was adequately prevented during the study.

Detection bias Blinding of outcome assessors (yes/no; assessed for each outcome separately): if knowledge of the allocated intervention was adequately prevented during the study.

Attrition bias Incomplete outcome data (adequate: yes/no; assessed for each outcome separately): if incomplete outcome (attrition and exclusions) data have been adequately addressed.

Reporting bias Selective outcome reporting (yes/no): if reports of the study were free of the suggestion of selective outcome reporting.

Other bias Other bias (yes/no): if the study was free of other problems (i.e. potential source of bias related to specific study design, premature termination of the study due to some data‐dependent process, extreme baseline imbalance) that could put it at high risk of bias.