Cantlie 1971.

Methods	RCT, 2‐arm trial with individual randomisation.
Participants	27 apparently healthy non‐anaemic pregnant women 17‐35 years of age from 4 participating obstetricians' private practice clinics from Montreal, Canada in their 1‐5th month of pregnancy with Hb 120 g/L or higher in first trimester and 110 g/L or higher in second trimester. Women with history of pathological blood loss or gross dietary imbalance were excluded.
Interventions	Participants were randomly assigned to 2 groups: group 1 received 39 mg elemental iron (Mol‐Iron®, ferrous iron) to be taken twice daily with meals (total daily 78 mg elemental iron); group 2 who received no iron tablets. As a co‐intervention, both groups received 1 tablet of multiple micronutrient supplement daily containing: 2 mg copper citrate, 6 mg magnesium stearate, 0.3 mg manganese carbonate, 1000 IU vitamin A , 500 IU vitamin D, bone flour 130 mg, 1 mg vitamin B1, 1 mg vitamin B2, 50 mg brewer yeast concentrate, 5 mg niacinamide, 25 mg vitamin C, 0.2 mg sodium iodide and 0.049 μg folate (naturally occurring). Duration of supplementation unclear. Setting and health worker cadre: the intervention was performed by obstetricians and hematologists at the McGill University Medical Clinic, Royal Victoria Hospital in Montreal, Canada. Participant, of higher SES, were of recruited from private obstetrical practices.
Outcomes	Maternal: Hb concentration, PCV, reticulocyte count, sedimentation rate, total white blood cell and differential counts, serum iron, unsaturated and total iron binding capacity, serum B12, serum and RBC folate at baseline and at 32, 36, 39th weeks and 7 days postpartum.
Notes	Supervision unclear. Compliance not reported. Gestational age at start of supplementation: mixed gestational age (1‐5th month of pregnancy). Anaemic status at start of supplementation: non‐anaemic. Daily iron dose: higher daily dose (60 mg elemental iron or more) (78 mg elemental iron). Iron release formulation: normal release iron supplement/not specified. Iron compound: Mol‐Iron®, ferrous iron. 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	Method not stated; "divided randomly".
Allocation concealment (selection bias)	Unclear risk	Not described.
Blinding of participants and personnel (performance bias) All outcomes	High risk	Women and staff were not blind to treatment allocation.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	It was not clear whether those assessing outcomes were aware of allocation, but it is unlikely that this possible lack of blinding affected the laboratory outcomes reported.
Incomplete outcome data (attrition bias) All outcomes	High risk	27 women were randomised. 26 mentioned in the discussion; denominators were not provided for the results.
Selective reporting (reporting bias)	Unclear risk	There is insufficient information to permit judgement.
Other bias	Unclear risk	Women in the intervention group had higher median serum folate levels at baseline (not sig).