Osendarp 2000.

Methods	RCT Sample size: 559 Inclusion criteria: mothers planned to remain at or near their residences in Dhaka for the delivery, did not have an established medical risk for reduced or excessive birth weight, and provided informed consent. Exclusion criteria: any violation of inclusion criteria
Participants	Pregnant women and newborns Age: at birth Country: Bangladesh Setting: selected areas of Dhaka city slums
Interventions	Type: supplementation of zinc Health workers provided 1‐week supply of supplements/placebo at a time. Women were instructed 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 during home visit. Urban specificity: none Level of factors tackled: individual Delivery: health workers provided weekly to the houses of women a 1‐week supply of zinc or placebo tablets weekly. Duration (years): 0.3 Comparison: IG: zinc amount based on twice the recommended daily intake for zinc during the last 2 trimesters of pregnancy, assuming low or moderate bioavailability, and was used previously in pregnant women without reports of adverse effects. The zinc content of the zinc tablets (zinc 31.0 mg/tablet; range 28.6–32.6; 20 tablets) CG: placebo tablets Measurement: baseline, 7 and 8 months' gestation, birth. Serum zinc concentrations, haemoglobin concentrations, and blood pressure assessed at baseline and again at 7 months' gestation during visits to the ICDDR, B Clinical Research and Service Centre. Information on dietary intake was collected at baseline and anthropometric measurements were made monthly from baseline until 8 months' gestation during home visits. Gestational age assessment, birth weight measurements, and infant anthropometric measurements were performed by trained physicians within 72 hours of birth. PROGRESS at baseline: SES and reproductive history of women. Categories for SES were developed using an index for urban populations on the basis of ownership of household durable goods. However, nutritional status data were not disaggregated by any of these variables.
Outcomes	Birth weight
Notes	No funding information Impact of the intervention: IG: birth weight: 2513 g, SD 390; length: 46.8 cm, SD 2.3 CG: birth weight: 2554 g, SD 393; length: 47.0 cm, SD 2.2
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Randomisation achieved by computer‐generated random‐letter assignment, and the codes remained unknown to both investigators and participants until study was completed.
Allocation concealment (selection bias)	Low risk	Randomisation achieved by computer‐generated random‐letter assignment, and the codes remained unknown to both investigators and participants until study was completed.
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Placebo was a cellulose tablet indistinguishable from the zinc supplement in both appearance and taste.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Codes for whether a participant was in the IG or IG remained unknown until the study was completed. Outcomes were objective measures that would be unlikely to be affected by knowing the assigned group.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Of the 559 women enrolled, 113 (20.2%) were lost to follow‐up before delivery (55 (20.4%) in the IG and 58 (20.0%) in the CG). As anticipated for this highly mobile population and despite the restrictions at enrolment, most losses to follow‐up (60) were due to out‐migration during the course of the study or to women leaving the area to deliver in their home villages. There were no differences in reasons for women being lost to follow‐up between the 2 groups.
Selective reporting (reporting bias)	High risk	No published protocol to establish this risk.
Other bias	Low risk	No other bias identified. Authors did not mention any competing effects of other interventions.
Similarity of outcome measures at baseline	Low risk	Maternal nutrition outcomes were measured prior to the intervention, and there were no important differences across study groups (only maternal nutritional outcomes were measured).
Similarity of baseline characteristics	Low risk	Baseline characteristics of the study and control providers were reported and similar across groups.
Protection against contamination	Low risk	Unlikely that the CG received the intervention as it was a supplementation intervention with randomisation of participants.