Chisholm 1966.

Methods	Women attending the antenatal clinic at their first visit before the 28th week of pregnancy were asked to participate in a randomised clinical trial to investigate the best method of preventing anaemia during pregnancy in Oxford (UK).
Participants	Women who had haemoglobin level less than 11 g per 100 mL and serum iron of less than 60 µg per 100 mL were not included in the trial and were treated immediately (n = 542).
Interventions	Half of the patient treated with ferrous gluconate (300 mg) 3 times daily (n = 183) and half with placebo tablets (n = 177). These groups were again divided into 3 groups; 1 group was given 500 µg (n = 61), or a high dose of 5 mg folic acid (n = 62) or a placebo (n = 59).
Outcomes	Mean haemoglobin level (360), red cell folate level and folate levels (360).
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "Random allocation of women to one of the 6 treatment groups".
Allocation concealment (selection bias)	Unclear risk	Quote: "Bottles containing the tablets were numbered by random selection". Comment: .insufficient information to permit judgement.
Blinding (performance bias and detection bias) All outcomes	Unclear risk	Quote: "code was not known while the patients were still on trial". Comment: participants were blinded.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Insufficient information to permit judgement.
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.