Harvey 2007.

Methods	RCT, 2 arms, individual randomisation.
Participants	13 apparently healthy non‐anaemic non‐smokers pregnant women aged 18‐40 years and < 14 weeks of gestation with singleton pregnancy recruited through local medical practitioners and the Maternity Department of the Norfolk and Norwich University Hospital, England, United Kingdom.
Interventions	Participants were randomly assigned to 1 of 2 groups: group 1 received 100 mg elemental iron (as ferrous gluconate) daily after food and group 2 received a placebo. Supplementation started at 16th week of gestation until delivery. Setting and health worker cadre: The intervention was performed by midwives and obstetricians at Maternity Department of the Norfolk and Norwich University Hospital in Norwich, United Kingdom.
Outcomes	Maternal: Hb, serum ferritin, transferrin receptor, plasma zinc, exchangeable zinc pool, zinc excretion and zinc absorption at 16, 24 and 34 weeks of gestation. Infant: birthweight (not reported).
Notes	Unsupervised. Compliance not reported. 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: higher daily dose (60 mg or more elemental iron). Iron release formulation: normal release preparation/unspecified. Iron compound: ferrous gluconate. 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)	Low risk	Coded bottles were provided by manufacturer.
Allocation concealment (selection bias)	Low risk	Supplied in coded opaque bottles.
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Described as a single‐blind, placebo‐controlled trial. Placebo and active tablets were described as identical. Women blinded not clear that staff were.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Investigators not blinded. Laboratory outcomes likely to be low risk of bias from blinding.
Incomplete outcome data (attrition bias) All outcomes	Low risk	No 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.