Paintin 1966.

Methods	RCT, 3 arms with individual randomisation.
Participants	180 primigravidae women with less than 20 weeks' gestation and Hb > 100 g/L attending antenatal clinic in Aberdeen Maternity Hospital, United Kingdom.
Interventions	Participants were randomly assigned to 1 of 3 groups: group 1 received 3 tablets containing 4 mg elemental iron each (total 12 mg daily); group 2 received 3 tablets containing 35 mg elemental iron (total 105 mg elemental iron daily); group 3 received placebo. Intervention was from week 20 to week 36 of gestation. Setting and health worker cadre: the intervention was performed by clinic and laboratory staff of the Obstetric Medicine Research Unit of Aberdeen Maternity Hospital and Castle Terrace Antenatal Clinic in Aberdeen, United Kingdom.
Outcomes	Maternal: Hb, HCT at baseline, and at weeks 20, 30, 36 of gestation and 7‐13 days postpartum; plasma volume at 30 weeks, total red cell volume, serum iron and total iron binding capacity at 30 weeks, subjective health and side effects at 30 weeks.
Notes	Unsupervised. Compliance estimated by measuring tablets returned. Authors report good compliance. Gestational age at start of supplementation: late gestational age (20 weeks' gestation at the start of supplementation). Anaemic status at start of supplementation: unspecified/mixed anaemia status at the start of supplementation. Daily iron dose: mixed doses (lower dose group ‐ 12 mg daily; higher dose group 105 mg daily). Iron release formulation: normal release preparation/not specified. Iron compound: not specified. Malaria setting: non‐malarial setting. As of 2011: Malaria: no risk.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Not described.
Allocation concealment (selection bias)	Low risk	Placebo‐controlled with sequentially numbered packages.
Blinding of participants and personnel (performance bias) All outcomes	Low risk	It was stated that women and staff were blind to treatment allocation. Placebo described as identical.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	It was stated that laboratory staff were blind to allocation until after the trial had been completed.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Less than 5%.
Selective reporting (reporting bias)	Unclear risk	There is insufficient information to permit judgement.
Other bias	Unclear risk	No other bias apparent.