Balmelli 1974.

Methods	It was a RCT in which women were randomised into 2 groups and recruited from Clinic for Female Medicine at the University of Bern (Switzerland). Average age for iron group was 27.8 years while for Iron + folic acid group was 26.9 years. Measurement were taken over the period of 12 weeks. Blood samples were taken at monthly intervals.
Participants	Pregnant women between 20‐25 weeks of pregnancy (n = 42).
Interventions	Group 1: ferrous sulphate 125 mg + vitamin B12 100 µg (n = 21). Group 2: ferrous sulphate 125 mg + folic acid 100 µg + vitamin B12 100 µg (n = 21).
Outcomes	Pre‐delivery haemoglobin level (n = 42), serum folate level (n = 42).
Notes	All the women were the residents of Switzerland for longer than a year. Participants were restricted to patients with a haemoglobin level between 10‐12 g%, suspected abnormal pregnancies or patients suffering from intercurrent illness were excluded from study.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Adequate sequence generation was not described in the text.
Allocation concealment (selection bias)	High risk	Quote " women were randomised into two groups". Comment: probably not done.
Blinding (performance bias and detection bias) All outcomes	High risk	Treatment was not blinded.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Reasons for exclusion were described. Attrition (21%) with reasons were mentioned in the study.
Selective reporting (reporting bias)	Unclear risk	Insufficient information to permit judgement.
Other bias	Unclear risk	No other bias identified but insufficient information available to fully assess this 'Risk of bias' domain.