Svanberg 1975.

Methods	RCT, 2 arms with individual randomisation.
Participants	60 healthy primiparous women attending antenatal care clinic in Goteborg, Sweden with uncomplicated pregnancy and less than 14 weeks of gestation and with Hb concentrations above 120 g/L who had not received iron supplements in the previous 6 months or parenteral iron at any previous time. Women whose Hb concentration fell below 100 g/L during the study period were excluded and received immediate therapy.
Interventions	Participants were randomly allocated to receive 200 mg of elemental iron (as a sustained release preparation of ferrous sulphate) daily or placebo from 12 weeks of gestation until 9 weeks post delivery. Setting and health worker cadre: the intervention was performed by physicians at the University of Göthenburg in Sweden.
Outcomes	Maternal: iron absorption measurements; Hb concentration, HCT, bone marrow haemosiderin, MCHC, total iron binding capacity, transferrin saturation at baseline, and at weeks 16, 20, 24, 28, 32, and 35; and 8‐10 weeks after delivery.
Notes	Unsupervised. Compliance measured by remaining pills count was 86 +/‐ 3%. 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: higher dose (more than 60 mg elemental iron daily). Iron release formulation: sustained release preparation of ferrous sulphate. 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)	Unclear risk	Not described.
Allocation concealment (selection bias)	Unclear risk	Not described.
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Participants, care provide, and outcome assessor blinded.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Participants, care provider, and outcome assessor blinded.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Less 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.