Siega‐Riz 2001.

Methods	RCT, 2 arms with individual randomisation.
Participants	429 non‐anaemic, iron replete women with less than 20 weeks of gestation attending who had not taken supplements containing iron in the last month, with a singleton pregnancy attending the prenatal clinic at the Wake County Human services in Raleigh, North Carolina, USA.
Interventions	Participants were randomly assigned to 1 of 2 groups: group 1 received multivitamin/mineral supplements containing 30 mg of iron (as ferrous sulphate) daily; group 2 received multivitamin/mineral supplements containing 0 mg of iron (no iron) until 29 weeks of gestation. Supplementation started on average at 12 weeks. The multivitamin/mineral supplement contained the following: 4000 IU vitamin A; 400 IU vitamin D; 70 mg vitamin C; 500 μg (0.5 mg) folic acid; 1.5 mg thiamine; 1.6 mg riboflavin; 17 mg niacin; 2.6 mg vitamin B6; 2.5 μg vitamin B1; 200 mg calcium; 100 mg magnesium; 1.5 mg copper; 15 mg zinc. Folic acid supplements were prescribed for all women who had received the positive pregnancy test until the first prenatal visit. Setting and health worker cadre: the intervention was performed by physicians at a clinic serving patients of a low socioeconomic group in Raleigh, North Carolina, United States of America.
Outcomes	Maternal: prevalence of anaemia, iron repletion and iron‐deficiency anaemia at 26‐29 weeks, side effects, compliance to treatment, iron status (Hb concentration, serum ferritin at 26‐29 weeks, preterm delivery. Infant: birthweight, proportion of low birthweight, small‐for‐gestational age.
Notes	Unsupervised. Compliance measured by pill counts and a questionnaire and was 66% in the iron group and 63% in the control group. Compliance was also measured by the Medication Event Monitoring System (MEMS) in a subsample of 100 women. Gestational age at start of supplementation: early gestational age (less than 20 weeks' gestation at the start of supplementation). Anaemic status at start of supplementation: non‐anaemic. Daily iron dose: lower daily dose (30 mg or less elemental iron daily). Iron release formulation: normal release preparation/unspecified. Iron compound: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)	Low risk	By using random number generator.
Allocation concealment (selection bias)	Low risk	Tretament provided in coded bottles by pharmacy.
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Described as double‐blind, randomised trial.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Low risk for laboratory outcomes.
Incomplete outcome data (attrition bias) All outcomes	High risk	More than 20% lost to follow‐up.
Selective reporting (reporting bias)	Unclear risk	There is insufficient information to permit judgement.
Other bias	Unclear risk	No other bias apparent.