Willoughby 1967.

Methods	RCT. 5‐arm trial.
Participants	3599 pregnant women with Hb above 100 g/L at their antenatal care clinic visit at Queen's Mother's Hospital in Glasgow, Scotland, United Kingdom. Women who reported not taken the tablets regularly were excluded as well as those diagnosed with anaemia during the study.
Interventions	Participants were randomly allocated to 1 of 5 interventions: group 1 received no prophylactic supplements; group 2 received 105 mg of elemental iron daily (as chelated iron aminoates); group 3 received 105 mg of elemental iron with 100 μg (0.1 mg) of folic acid; group 4 received 105 mg of elemental iron daily with 300 μg (0.3 mg) of folic acid; group 5 received 105 mg elemental iron daily with 450 μg (0.45 mg) of folic acid. Starting and ending time of supplementation variable. Setting and health worker cadre: the intervention was performed by a team of nurses and physicians at the Antenatal Clinic of the Queen Mother's Hospital in Glasgow, United Kingdom.
Outcomes	Maternal: Hb concentration at baseline and in every visit, at early puerperium and during postnatal visit; incidence of obstetric complications. incidence of megaloblastic anaemia. Infant: Hb and whole blood folate levels a 6 weeks of age. Incidence of neonatal complications.
Notes	Unsupervised. Groups 3‐5 were merged for the purposes of this review. Women were excluded from the trial and the analysis if they were diagnosed as anaemic. Compliance not reported. Gestational age at start of supplementation: mixed gestational age at the start of supplementation. Anaemic status at start of supplementation: mixed anaemia status (Hb > 100 g/L). Daily iron dose: higher daily dose (more than 60 mg elemental iron daily). Iron release formulation: not clear? normal release preparation/unspecified. Iron compound: chelated iron aminoates. 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)	Unclear risk	Not described.
Blinding of participants and personnel (performance bias) All outcomes	High risk	No blinding. Women with anaemia or non‐compliant were withdrawn from the study.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Low risk for laboratory outcomes.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Less than 20% losses to follow‐up. However, women were excluded from the trial and the analysis if they were diagnosed as anaemic.
Selective reporting (reporting bias)	Unclear risk	There is insufficient information to permit judgement.
Other bias	Unclear risk	No other bias apparent.