Study	Reason for exclusion
An 2001	313 healthy pregnant women at their fifth month of gestation enrolled in the hospital for prenatal care in Beijin, China, were given fortified biscuits containing (vitamin D), (vitamin D + calcium), (vitamin D + calcium + iron), (vitamin D + calcium + iron + zinc). Only 1 woman selected from the same hospital (no fortified biscuits given) as control comparison. The study indicated quasi‐randomised study, which there was no randomised sequence generation performed and allocation was by the order of hospital visits.
Appelbaum 1979	The effect of diet supplementation throughout pregnancy on third‐trimester amniotic fluid growth‐supporting activity was studied in 100 African women; 32 were given zinc supplementation, 22 each animal and vegetable supplements, respectively, and 24 served as control subjects. Zinc level was measured among the groups and the inhibitory of zinc was conducted in vitro testing of the amniotic fluid collected. The study design did not indicate randomised controlled trial and the outcome was the zinc level of amniotic fluid only.
Christian 2001	A placebo‐controlled trial in Nepal was conducted on 202 women who reported to be night blind during pregnancy. They were randomly assigned in a double‐blind manner, stratified on vitamin A, ß‐carotene, or placebo receipt, to receive 25 mg Zn or placebo daily for 3 weeks. The participant selection was on women who had night blindness and there was no prespecified outcomes reported related to pregnancy except for vision restoration of pregnant women.
Fawzi 2005	Pregnant women who were HIV‐infected, who resided in Dar es Salaam, Tanzania, at the time of the baseline interview, and who intended to stay in the city until delivery and for were considered. 400 HIV‐infected pregnant women were between 12 and 27 weeks of gestation were randomly assigned to daily oral supplementation with either 25 mg Zn or placebo between recruitment and 6 weeks after delivery. The population selected for the trial were not in healthy state of condition.
France 2004	Healthy pregnant women (n = 100) receiving prenatal care between 12 and 16 weeks of gestation in the Obstetric Departments of Grenoble and Lyon Hospitals in France participated in a double‐blind, randomised, placebo‐controlled trial. The intervention was micronutrients supplement or placebo. The micronutrients contained vitamin C (60 mg), ß‐carotene (4.8 mg), vitamin E (10 mg), thiamin (1.4 mg), riboflavin (1.6 mg), niacin (15 mg), pantothenic acid (6 mg), folic acid (200 mg), cobalamin (1 mg), Zn (15 mg as citrate), Mg (87.5 mg as glycerophosphate), Ca (100 mg as carbonate). Zinc was not given separately as the main intervention.
Hambidge 1983	A longitudinal study (monthly intervals) in 46 pregnant middle‐income women. 10 of the women received a daily supplement of 15 mg Zn and the rest of the women did not receive any zinc supplement. The design was an observational study with no mention of randomisation or allocation to zinc or no‐zinc groups.
India 1993	90 pregnant women were randomly assigned to control (A) and 120 pregnant women were randomly assigned to zinc treated (B) groups. Group B women were administered a single daily dose of 45 mg zinc as a 200 mg zinc sulphate tablet (Zinfate, Yash Pharma) from the day of reporting till delivery. The control group women were not provided with zinc supplementation. The total number of subjects finally selected in group A served as control was 62, and that in Gp. B, was 106. The study design was a quasi‐randomised study and with large discrepancies in numbers of participants at baseline and follow‐up.
Kynast 1986	A randomly selected study group of 179 pregnant women and a control group of 345 pregnant women were given zinc aspartate. This study investigates the prophylactic effectiveness of zinc replacement in reducing the overall complication rate for both mother and fetus and in particular for large‐for‐date and small‐for‐date infants. The study design was a quasi‐randomised study and allocation was done by alternation.
Mahmoudian 2005	A total of 118 anaemic women were recruited in this randomised controlled trial. Both groups received 100 mg elemental iron daily. The intervention group received an additional dose of 15 mg zinc every day for a period of 12 weeks while the control group received placebo. The participants were all anaemic women and outcomes were haemoglobin concentration only.
Makola 2003	This study was a randomised, placebo‐controlled double‐blind effectiveness trial of a micronutrient‐fortified dietary supplement conducted in pregnant women in Tanzania. Pregnant women who believed that they were between 12 and 34 weeks pregnant were invited to participate in the study. The intervention was micronutrient supplement (orange‐flavoured micronutrient‐fortified powdered beverage mix containing 11 micronutrients, including zinc) in comparison to placebo. Women with gestation greater than 26 weeks were included in the study and zinc was not provided separately as an supplemented intervention.
Naher 2012	A total of 200 pregnant women, age ranging between 18‐40 years and gestational age ranging from 37‐42 weeks were selected for a cross‐sectional study in Bangladesh. Among them, 100 were advised to take 61.8 mg zinc daily and the others did not. The study design was an observational study and not a randomised controlled trial.
Nishiyama 1999	38 Japanese women at the second trimester of pregnancy had haemoglobin concentrations below 11.0 g/dL and 32 of 38 had normocytic erythrocytes. These women were divided into 3 groups, and they were compared for their haematological status and serum IGF‐I levels before and after iron (Group A) or Zn (Group B) or iron plus Zn (Group C) supplementation. The the women were anaemic and the study design was a clinical controlled trial where women could chose 1 of 3 intervention groups.
Nogueira 2003	74 low‐income pregnant adolescents in Brazil ranging from 13‐18 years of age received supplementation of (folic acid + iron), (folic acid + zinc sulphate + iron) or only (iron). The pregnant adolescents were divided into 5 groups. The study method was based on longitudinal design and zinc plasma concentration was measured as to support the folic acid metabolism.
Van Vliet 2001	The study was an open, randomised study, using a cross‐over approach for 2 sources of vitamin A (i.e. liver paste and retinyl palmitate containing oil) and a parallel approach for 3 dose levels of vitamin A (i.e. 3.0, 7.5, and 15 mg vitamin A) for women between 19‐47 years of age. Pregnant women were excluded in the study. The intervention did not use zinc supplements or any zinc constituent supplements.
Villamor 2006	Pregnant women with HIV and the HIV status of their babies was assessed at birth and at 6 weeks postpartum at Dar es Salaam Tanzania. Women 12–27 weeks of gestation were randomly assigned to receive a daily oral dose of 25 mg zinc or placebo from the day of the first prenatal visit until 6 weeks postdelivery. All the participants were infected with HIV.
Yalda 2010	Single‐blind randomised clinical control trial conducted in Kurdistan region, Iraq. 100 anaemic pregnant women were selected to receive, first group (A), supplemented daily with 120 mg iron and second group (B) received 120 mg iron + 22.5 mg zinc. The pregnant women were all diagnosed with anaemia and the outcome were to assess the improvement of anaemic condition.