Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: “Enrolled subjects were randomly assigned to either a supplemented or non supplemented group”Comment: Insufficient information to determine level of bias
Allocation concealment (selection bias)	Unclear risk	Comment: Insufficient information to permit judgement
Blinding of participants and personnel (performance bias)	Unclear risk	Comment: Insufficient information to permit judgement
Blinding of outcome assessment (detection bias)	Unclear risk	Comment: Insufficient information to permit judgement
Incomplete outcome data (attrition bias)	Low risk	Quote: “One woman in each group lost her fetus before 30 weeks of gestation and one woman in the supplemented group missed her infusion date because of travel. However, she continued participating in the study by taking her dietary supplement and her pregnancy outcome data are included”
Selective reporting (reporting bias)	Unclear risk	Comment: Published protocol not found. The outcomes specified in the methodology section have been reported in the results section
Other bias	Low risk	Comment: No other potential sources of bias reported
Was the allocation sequence adequately generated?	Unclear risk
Was the allocation adequately concealed?	Unclear risk
Were baseline outcome measurements similar?	Unclear risk
Were baseline characteristics similar?	Unclear risk
Were incomplete outcome data adequately addressed?	Unclear risk
Was knowledge of the allocated intervention adequately prevented during the study?	Unclear risk
Was the study adequately protected against contamination?	Unclear risk
Was the study free from selective outcome reporting?	Unclear risk
Was the study free from other risk of bias?	Unclear risk