Quintero 2004.

Methods	RCT, 2‐arm trial with individual randomisation
Participants	107 healthy pregnant women with 6‐20 wks of gestation who had not received iron supplements during the current pregnancy attending 19 health units in the State of Morelos, Mexico.
Interventions	Participants were randomly assigned by block pairs (anaemic and not anaemic) to receive either 120 mg of elemental iron (as ferrous sulphate) in a single dose daily or once weekly for 10 wks. Setting and health worker cadre: the intervention was performed by physicians at primary healthcare clinics in Morelos, Mexico.
Outcomes	Hb concentration, prevalence of anaemia and nutrient consumption at baseline and after 10 wks of supplementation were measured. Data on none of the prespecified outcomes of this review were available. Gestational ages at recruitment and follow‐up were very variable among the participants and results are therefore difficult to interpret. Laboratory method for ferritin concentration: ferritin not measured.
Notes	Data from this study have not been included in the analyses. 1. By gestational age at start of supplementation: early (supplementation started before 20 wks' gestation or prior to pregnancy). 2. By anaemia status at baseline: unspecified/mixed anaemia status at start of supplementation. 3. By weekly iron dose in the group receiving intermittent supplementation: low weekly dose of iron in the intermittent group (120 mg elemental iron or less per wk). 4. By release speed of iron supplements: not specified/unreported/unknown. 5. By bioavailability of the iron compound relative to ferrous sulphate: equivalent or lower: ferrous sulphate. 6. By intermittent iron supplementation regimen: once a wk. 7. By malaria endemicity of the area in which the trial was conducted: not specified/unreported/unknown. Study carried out in malaria risk‐free parts of countries that has malaria risk in other parts. As of 2011: malaria risk due almost exclusively to Plasmodium vivax exists throughout the year in some rural areas. There is moderate risk in some localities in the states of Chiapas and Oaxaca; very low‐risk localities are also found in the states of Chihuahua, Durango, Nayarit, Quintana Roo and Sinaloa. Source of funding: Health Department State of Morelos, Mexico; National Institute of Public Health, Curenavaca, Mexico.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	By computer‐generated random numbers.
Allocation concealment (selection bias)	High risk	Participants were allocated to the groups consecutively by pairs.
Blinding of participants and personnel (performance bias) All outcomes	High risk	Different regimens compared. Women and staff would be aware of treatment allocation.
Blinding of outcome assessment (detection bias) Laboratory outcomes	Low risk	Laboratory outcomes were unlikely to have been affected by lack of blinding (not reported in the review).
Blinding of outcome assessment (detection bias) Side effects and compliance	Unclear risk	Not clear if data on side effects were collected (not reported).
Incomplete outcome data (attrition bias) All outcomes	High risk	107 women recruited and complete data available for 77 women.
Selective reporting (reporting bias)	Unclear risk	There is insufficient information to permit judgement.
Other bias	Low risk	The study appears to be free of other sources of bias.