Liu 2003.

Methods	RCT. 3‐arm trial with additional non‐random control group.
Participants	395 healthy, anaemic and non‐anaemic, pregnant women attending prenatal care at 2 outpatient clinics at Changji Hospital and Shihezi Maternal and Child Health Station in Xianjiang, China. Women with Hb < 80 g/L were excluded. Maternal age was 25.15 ± 2.28 years.
Interventions	Participants were randomly assigned to 1 of 3 groups: group 1: 60 mg elemental iron as ferrous sulphate and 250 μg (0.25 mg) of folic acid daily; group 2: 120 mg of elemental iron (as ferrous sulphate) and 500 μg (0.5 mg) of folic acid daily; group 3: 120 mg elemental iron (as ferrous sulphate) and 500 μg (0.5 mg) of folic acid once weekly. A control group that received no iron was composed of women who did not want to participate in the study and did not receive any iron supplements. Since the allocation of the control group was not randomised, we included this study in our comparisons of the effects of intermittent vs daily iron supplementation. Setting and health worker cadre: the intervention was performed by physicians and researchers in 2 outpatient clinics of the department of Obstetrics in Changji Hospital and Shihezi Maternal and Child Health Station in Xianjiang, China.
Outcomes	Maternal: Hb concentration at 3, 5, 8 months and at term; serum ferritin concentrations at 3 months and at term in a subgroup; side effects. Weight at entry and at term (not used in the review). Laboratory method for ferritin concentration: not reported.
Notes	Unsupervised. Iron supplementation is not mandatory for women in China, if they have a Hb concentration > 80 g/L. Compliance for group 1 (daily 60 mg Fe), group 2 (daily 120 mg Fe) and group 3 (weekly 120 mg Fe) were 77%, 75% and 86% respectively. 1. By gestational age at start of supplementation: unspecified gestational age or mixed gestational ages at the start of supplementation. 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, including Plasmodium falciparum malaria, exists in Yunnan and to a lesser extent in Hainan. There is no malaria risk in urban areas. Source of funding: not reported.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	High risk	Method unclear. Non‐supplemented group was self‐selected.
Allocation concealment (selection bias)	Low risk	Sealed closed envelopes were used.
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	Outcome assessor reported to be blinded. Laboratory outcomes unlikely to be affected by blinding.
Blinding of outcome assessment (detection bias) Side effects and compliance	High risk	Women's reporting of side effects and compliance may have been affected by lack of blinding.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Less than 20% lost to follow‐up but there were missing data for some outcomes (only 2 arms of this trial included in the analyses).
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.