Chanarin 1971.

Methods	Quasi‐RCT. 5‐arm trial with individual randomisation.
Participants	251 women attending antenatal clinic at St Mary's Hospital, London, United Kingdom before 20th week of gestation.
Interventions	Participants were allocated by sequence to 1 of 5 groups: group 1: oral dose of 30 mg of elemental iron (as ferrous fumarate) daily; group 2: oral dose of 60 mg of elemental iron (as ferrous fumarate) daily; group 3: oral dose of 120 mg of elemental iron (as ferrous fumarate) daily; group 4: placebo; group 5: 1 g of iron (Imferon, 4 x 250 mg) intravenously before week 20, and thereafter oral 60 mg of elemental iron (as ferrous fumarate) daily (not included in this review). Supplementation started at 20th week until 37th week. Only the data related to comparisons of group 1: oral dose of 30 mg of elemental iron daily with group 4: placebo are used in this review given that no data for the other groups could be desegregated. Setting and health worker cadre: the intervention was performed by obstetricians and pathologists at the antenatal clinic of St. Mary's Hospital in London, United Kingdom.
Outcomes	Maternal: full blood count, serum iron at 20, 25, 30 and 37th week. Sternal marrow aspiration at 37 weeks; antepartum haemorrhage, threatened abortion, urinary tract infection, fetal abnormalities, pregnancy hypertension, premature delivery and puerperal infection measured but not reported by groups. Infant: birthweight (not reported by groups).
Notes	Compliance not reported. Gestational age at start of supplementation: late gestational age (supplementation started at 20 weeks' gestation). Anaemic status at start of supplementation: unspecified/mixed anaemia status. Daily iron dose: different doses in different arms of trial (group 1 lower daily dose: 30 mg; group 2 and 3 higher daily dose 60 mg or more). Iron release formulation: normal release preparation/unspecified. Iron compound: ferrous fumarate. 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)	High risk	Quasi‐randomised study, assignment by sequence.
Allocation concealment (selection bias)	High risk	Women were "allocated in sequence to one of five groups"; allocation order could therefore be anticipated.
Blinding of participants and personnel (performance bias) All outcomes	Low risk	1 of 5 groups was given an IV medication (not included in this review). The other 4 were given iron or placebo tablets and for the oral medication it was stated that women and staff were not aware of which treatment women were receiving.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Women who developed anaemia were withdrawn from the study. It was not clear at what point investigators were aware of treatment allocation.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	It was not clear exactly how many women were randomised; there were approximately 50 in each of 5 groups. 11 women (9 from the placebo group) were withdrawn and given treatment for anaemia "after allowance had been made for the subjects dropping out of the study... there were just under 50 subjects in each group".
Selective reporting (reporting bias)	Unclear risk	There is insufficient information to permit judgement.
Other bias	Unclear risk	No other bias apparent.