Kuizon 1979.

Methods	RCT, 4 groups (with supplementation depending on Hb levels at baseline) individual randomisation.
Participants	385 pregnant women attending antenatal care at government health centres in Greater Manila area, Philippines. Mean gestation at recruitment was approximately 21 weeks until delivery. Women were assessed at baseline and women with anaemia ( Hb < 120 g/L in 1st and < 110 g/L in 2nd trimester) received a higher dose of supplements.
Interventions	Participants were randomly assigned to 1 of 4 groups: group 1 received placebo (anaemic and non‐anaemic women received 1 placebo capsule); group 2 received 65 mg of elemental iron ( as 325 mg ferrous sulphate) women received either 1 or 3 oral tablets daily; group 3 received 100 mg ascorbic acid (either 1 or 3 oral tablets daily); group 4 received 65 mg elemental oral iron (as ferrous sulphate) plus 100 mg ascorbic acid ‐ women received either 1 or 3 tablets. Supplementation started from recruitment in 1st and second trimester until delivery. Setting and health worker cadre: the intervention was performed by health centre staff at government health centres and maternity clinics in the greater Manila area, Manila, Phillipines.
Outcomes	Mean Hb concentration at 32 and 39 weeks (for women anaemic and not anaemic at baseline), HCT at 32 and 39 weeks, serum iron at 32 and 39 weeks, transferring saturation levels at 32 and 39 weeks.
Notes	Attrition in this study was very high (half of the women were lost to follow‐up by 32 weeks' gestation and more than 75% by term). For this reason we have not included data from this study in our data and analyses tables. Gestational age at start of supplementation: mixed gestational age at the start of supplementation (mean gestation at start of supplementation was 21 weeks). Anaemic status at start of supplementation: mixed anaemia status (dose depended on Hb level at baseline). Daily iron dose: higher daily dose (greater than 60 mg of elemental iron daily). Iron release formulation: normal release preparation/unspecified. Iron compound: ferrous sulphate. Malaria setting: yes. As of 2011: Malaria risk exists throughout the year in areas below 600 m, except in the 22 provinces of Aklan, Albay, Benguet, Biliran, Bohol, Camiguin, Capiz, Catanduanes, Cavite, Cebu, Guimaras, Iloilo, Northern Leyte, Southern Leyte, Marinduque, Masbate, Eastern Samar, Northern Samar, Western Samar, Siquijor, Sorsogon, Surigao Del Norte and metropolitan Manila. No risk is considered to exist in urban areas or in the plains. P. falciparum resistant to chloroquine and sulphadoxine–pyrimethamine reported. Human P. knowlesi infection reported in the province of Palawan.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Not described.
Allocation concealment (selection bias)	Unclear risk	"randomly assigned."
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Placebo was provided but women received different doses (and number of tablets).It was not clear if staff were aware of allocation.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	It was not clear if outcome assessment was blind. Low risk for laboratory outcomes.
Incomplete outcome data (attrition bias) All outcomes	High risk	Very high attrition. 679 women recruited. In non‐anaemic women, 189/385 followed up (49%). In anaemic group  146/294 (50%) followed up at 32 weeks by 39 weeks only 94/385 non‐anaemic women followed up (24%) and 60 in anaemic group (20%).
Selective reporting (reporting bias)	Unclear risk	There is insufficient information to permit judgement.
Other bias	High risk	The reasons for the very high levels of attrition were not explained (except that some women delivered before term). The very high loss to follow‐up means that results are very difficult to interpret.