De Benaze 1989.

Methods	RCT, 2‐arm trial with individual randomisation.
Participants	191 non‐anaemic pregnant women with 12‐18 weeks of gestation attending antenatal care clinic at the Maternity at Poissy Hospital, Paris, France. Exclusion criteria included women who had taken iron or folate supplements in the prior 6 months and those with language barriers for proper communication. Supplementation started at 12‐18 weeks until delivery.
Interventions	Participants were randomly allocated to 1 of 2 groups: group 1: daily intake of 45 mg of elemental iron (as ferrous betainate hydrochloride) (15 mg elemental iron per tablet); group 2: placebo tablets. Setting and health worker cadre: the intervention was performed by physicians at the Maternity Ward of Poissy Hospital, Poissy, France.
Outcomes	Maternal: Hb, MCV, serum iron, total iron binding capacity, transferrin saturation, serum ferritin at baseline, at 5 months, at 7 months, at delivery and 2 months postpartum.
Notes	Unsupervised. Serum ferritin values presented as arithmetic and geometric means. No SD in transformed ferritin values is presented. Women in the placebo group were prescribed treatment after delivery thus not allowing comparisons at 2 months postpartum among the groups. Compliance reported as good. Gestational age at start of supplementation: early gestational age (supplementation started before 20 weeks' gestation). Anaemic status at start of supplementation: non‐anaemic. Daily iron dose: medium daily dose (45 mg elemental iron). Iron release formulation: normal release preparation/not specified. Iron compound: ferrous betainate hydrochloride. 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	Randomised but method used unclear.
Allocation concealment (selection bias)	Low risk	Placebo‐controlled trial. Active and placebo tablets were in identical packaging and packages were provided randomly.
Blinding of participants and personnel (performance bias) All outcomes	Low risk	(Assessment from translated notes). Placebo‐controlled trial with active and placebo supplements in identical packaging and tablets were identical in appearance.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Placebo‐controlled trial and laboratory outcomes.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Less than 20% losses to follow‐up.
Selective reporting (reporting bias)	Unclear risk	There is insufficient information to permit judgement.
Other bias	Unclear risk	No other bias apparent.