Bangladesh 2000.

Methods	A double‐blind, randomised, placebo‐controlled trial.
Participants	559 pregnant women between 12 and 16 weeks' gestation, from Dhaka city slums. The 446 women who completed follow‐up had a mean baseline serum zinc level of 15.3 [SD 4.3] µmol/L (similar to those lost to follow‐up). Energy intakes were low at 4 months' gestation (median 6065 kJ/day). A total of 559 pregnant women from selected areas of Dhaka city slums were identified between 12 and 16 weeks of gestation through an established pregnancy identification system between March and June 1996. Women were included if they remain at or near their residences in Dhaka for the delivery without established medical risk for reduced or excessive birthweight (e.g. hypertension, renal disease, or diabetes). The 446 women who completed follow‐up had a mean baseline serum zinc level of 15.3 [SD 4.3] µmol/L (similar to those lost to follow‐up). Energy intakes were low at 4 months' gestation (median 6065 kJ/day).
Interventions	Zinc was given twice the recommended daily intake during the last 2 trimesters of pregnancy. The zinc tablets contained (31.0 mg Zn/tablet; range: 28.6–32.6) and placebo tablets contained (0.0 mg Zn/tablet; range: 0.0–0.1) were was verified and confirmed by 2 independent laboratories. The placebo was a cellulose tablet indistinguishable from the zinc supplement in both appearance and taste. Health workers provided a 1‐week supply of zinc or placebo tablets (ACME Ltd, Dhaka) to the houses of the women weekly and instructed the women to consume 1 tablet daily between meals and not together with other vitamin or mineral supplements. Compliance was assessed by counting the remaining tablets in each strip at the next visit. Unannounced compliance checks between regular visits were performed monthly in subsamples of 10% of the study participant. Zinc: 30 mg elemental zinc/day (n = 269 [214]) . Placebo: n = 290 [232]).
Outcomes	Maternal outcomes Serum zinc concentrations at 7 months' gestation; haemoglobin concentrations at 7 months' gestation; blood pressure at 7 months' gestation; preterm birth and gestational age; stillbirth. Neonatal outcomes Birthweight; low birthweight, < 2500 g, < 2000 g, < 1500 g; gestational age (weeks); prematurity,< 37 weeks, < 32 weeks; small‐for‐gestational age; length (cm), head circumference (cm), chest circumference (cm), and mid‐upper arm circumference (mm).
Notes	Adherence: percentage of days during follow‐up that a woman reported having consumed a supplement was 86%. Final sample size of 410 infants was sufficient to detect a 110 g difference in birthweight.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	"computer‐generated random letter assignment."
Allocation concealment (selection bias)	Unclear risk	"randomly assigned" ‐ no details given regarding allocation concealment.
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Both investigators and participants were blinded.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Not specifically mentioned but assessors were also likely to have been blinded.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	113/559 (20.2%) women were lost to follow‐up before birth; (55 (20.4%) in the zinc group and 58 (20.0%) in the placebo group) ‐ most (60) due to migration out of the area. By 13 months follow‐up, 383 (68.5%) infants remained in the trial, with only 168 of these infants being included in the 13‐month analysis.
Selective reporting (reporting bias)	Unclear risk	Some primary outcomes such as mode of birth not reported.
Other bias	Low risk	No apparent source of other bias.