Baumslag 1970.

Methods	This was a randomised trial conducted on all pregnant women who were attending antenatal clinics at the Baragwanath and South Rand Hospitals, Johannesburg (South Africa). Pregnant women were allocated into 3 interventions groups based on random numbers.
Participants	All pregnant women attending antenatal clinics at Baragwanath and South Rand Hospitals, Johannesburg (n = 355).
Interventions	Group 1 received 200 mg of iron by mouth (n = 115). Group 2 received 5 mg of folic acid daily by mouth in addition to the iron (n = 127). Group 3 received 50 µg of vitamin B12 by mouth in addition to the folic acid and iron (n = 113).
Outcomes	Birthweight was measured.
Notes	Birthweight was analysed separately for Bantu participants and white participants. In the white participants supplementation was started after the 24th week, while supplementation in Bantu participants was started after 28th week. We compared the data of group 1 with group 2 only.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "patients were allocated by random numbers to three groups".
Allocation concealment (selection bias)	Unclear risk	Insufficient information about allocation concealment.
Blinding (performance bias and detection bias) All outcomes	Unclear risk	Insufficient information about blinding.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Insufficient information about exclusion and attrition.
Selective reporting (reporting bias)	Low risk	The study has mentioned data on all outcome measure mentioned as objective.
Other bias	Unclear risk	No other bias identified but insufficient information available to fully assess this 'Risk of bias' domain.