UK 1991b.

Methods	A double‐blind, RCT.
Participants	152 women resident in Scunthorpe Health District who booked for care before the 18th week of gestation, and who were booked for delivery at either Scunthorpe Maternity Home or at Scunthorpe General Hospital, were recruited for the study. 134 women completed the trial.
Interventions	Women were randomly assigned to 2 groups, X and Y. The the supplements were prepared by Smith Kline and French. The spansules contained 150 mg of FeSO4 and 0‐5 mg of folic acid for Group X. For Group Y, 62 mg of zinc sulphide was added to the 150 mg of FeSO4 and 0‐5 mg of folic acid . Participants were asked to take 1 spansule per day. Haematological tests were undertaken on entering the study and at the 28th week of gestation. Group X: iron + folic acid (n = 62). Group Y: iron + folic and zinc: (n = 72).
Outcomes	Low birthweight < 2500 g; birthweight > 3500 g; congenital malformations; stillbirth/neonatal death.
Notes	Adherence was not reported.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Not reported.
Allocation concealment (selection bias)	Unclear risk	Not reported.
Blinding of participants and personnel (performance bias) All outcomes	Low risk	"double blind."
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Not reported.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Losses to follow‐up: 18/152 (12%) due to GI effects, aborted or woman moved, leaving 72 in the zinc group and 62 in the control group.
Selective reporting (reporting bias)	High risk	No maternal outcomes reported.
Other bias	Low risk	No apparent risk of other bias.