Liu 2000.

Methods	RCT with 3‐arms, and individual randomisation.
Participants	300 pregnant women with 24‐28 weeks of gestation with no had organic disease and Hb level higher than 100 g/L who received antenatal examinations in Second Affiliated Hospital, Zhujiang Hospital, the First Military Medical University, Guangzhou, China from January 1998 to January 1999.
Interventions	Participants were randomly assigned to 1 of 3 groups: group 1 received 1 tablet daily containing 100 mg elemental iron (as ferrous sulphate sustained‐release) with 500 mg vitamin C and B‐complex vitamins (amounts not reported) administered orally for 4 consecutive weeks; group 2 received conventional iron supplement (as 300 mg ferrous sulphate) administered 3 times a day to meals for 4 consecutive weeks; group 3 did not receive any iron supplementation. Setting and health worker cadre: intervention and outcome assessment were conducted by physicians from the Obstetric & Gynecology Department, Zhujiang Hospital, the First Military Medical University, Guangzhou, China.
Outcomes	RBC, Hb and serum ferritin at baseline at after 4 weeks of intervention and before delivery. Anaemia, iron deficiency, fatigue, dizziness, shortness of breath, and pale mucous membranes and skin, tinnitus, presence of stomatitis or glossitis, premature birth, average Apgar score, congenital malformations. Side effects reported: nausea and loss of appetite, severe gastrointestinal reactions including vomiting, abdominal pain, and diarrhoea, metallic taste in the mouth, black staining of their teeth. Blood tests and serum ferritin measurement were performed for the gravidas after 4 and 8 weeks of supplementation and before delivery. The Apgar scoring and physical examinations were performed for the newborns after delivery.
Notes	Gestational age at start of supplementation: late gestational age (supplementation started at 20 weeks' gestation or later). Only groups included in the comparisons are group 2 and group 3 who did not receive supplements. Anaemic status at start of supplementation: non‐anaemic. Daily iron dose: high daily dose (60 mg or more mg iron daily). Iron release formulation: normal and slow release preparation for group 1 (not included in the comparisons in this review). Iron compound: ferrous sulphate. Malaria setting: yes. As of 2011: Malaria risk, including P. falciparum malaria, exists in Yunnan and to a lesser extent in Hainan. P. falciparum resistance to chloroquine and sulphadoxine–pyrimethamine reported. Limited risk of P. vivax malaria exists in southern and some central provinces, including Anhui, Ghuizhou, Henan, Hubei, Jiangsu. There is no malaria risk in urban areas.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Reported as randomised but method unclear.
Allocation concealment (selection bias)	Unclear risk	There is insufficient information to permit judgement.
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	No blinding mentioned but this was a placebo‐controlled trial.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Low risk for laboratory outcomes.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Data reported as complete for all the participants reported as randomised.
Selective reporting (reporting bias)	Unclear risk	There is insufficient information to permit judgement.
Other bias	Low risk	There were no significant differences in terms of age, gestational age, body weight, and H level among the 3 groups (all P > 0.05).