Hood 1960.

Methods	RCT, 3 arms, individual randomisation.
Participants	75 consecutive apparently healthy pregnant women with 32‐34 weeks of gestation attending the maternity clinic at St Anthony's Hospital, Oklahoma City, Oklahoma, USA.
Interventions	Participants were randomly divided in 3 groups: group 1 served as control and received no treatment; group 2 received 220 mg elemental iron (as ferrous sulphate) daily; and group 3 received 55 mg elemental iron (as sustained release ferrous sulphate) daily. Supplementation started at 32‐34 weeks of gestation until delivery. Setting and health worker cadre: the intervention was performed by obstetricians at the Department of Obstetrics and Gynecology of St. Anthony's Hospital in Oklahoma City, Oklahoma, United States of America.
Outcomes	Maternal: Hb, HCT, incidence and severity of side effects on a weekly basis until delivery.
Notes	Unsupervised. For any iron vs no treatment comparison groups were merged. Compliance not reported. Gestational age at start of supplementation: late gestational age (supplementation started after 20 weeks' gestation). Anaemic status at start of supplementation: unspecified/mixed anaemia. Daily iron dose: medium dose (55 mg elemental iron) and higher dose (220 mg elemental iron). Iron release formulation: sustained release preparation and normal release preparation/not specified. Iron compound: ferrous sulphate and sustained release ferrous sulphate. 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	Neither participant nor provider blinded.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Outcome assessor unclear. Low risk for laboratory outcomes but uncertain risk of bias for reported side effects.
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.