USA 1985.

Methods	A double‐blind, RCT.
Participants	138 Hispanic teenagers who were under 17 years of age and were not over 27 weeks' gestation and who were attending prenatal clinic at Los Angeles were recruited for the study. The mean dietary zinc intakes among these women were about 50% of the RDA. according to LMP. These teenager did not have diabetes, heart, renal or thyroid disease. All participants were agreed to take the test vitamin and mineral supplement as prescribed, return to the clinic for 2 interviews with the research nutritionist, allow 3 blood and 2 hair samples to be taken, and permit the nutritionist to obtaining the study provided by the staff from their clinic, delivery, and infant records.
Interventions	The teenagers were randomly assigned to control group and treatment group. For treatment group, they received daily vitamin and mineral supplement in a single capsule providing (20 mg) of zinc. The control group received a capsule that did not contain zinc. The supplements composed of 8000 IU vitamin A, 400 IU vitamin D, 30 IU vitamin E, 2 mg thiamin mononitrate, 2 mg riboflavin, 20 mg niacinamide, 5 mg pyridoxine HCl, 1 mg folic acid, 10 µg vitamin B12 (cyanocobalamin), 10 mg pantothenic acid, 60 mg vitamin C, 100 mg calcium (as carbonate), 20 mg iron (as ferrous fumarate), 50 mg magnesium (as oxide), 1 mg manganese (as sulphate) and 150 µg iodine (as potassium iodide). The capsules between the 2 groups were identical in taste and appearance by (Pharmavite Pharmaceuticals Coporation, Pacoima, CA). The teenagers were instructed to take the capsule with their evening meal rather than at breakfast. In addition, 108 mg iron/day was prescribed routinely at 20 weeks' gestation. Zinc with vitamin and mineral group: (n = 70). Vitamin and mineral group: (n = 68).
Outcomes	Infant weight; placental weight; pregnancy‐induced hypertension; meconium‐stained amniotic fluid; birthweight > 2500 g; Apgar scores; preterm birth; fetal death; plasma zinc; haemoglobin; haematocrit; ferritin levels; folacin levels.
Notes	Adherence: defined as those in study long enough to take supplements for more than 60 days and who then returned to the pharmacy for 1 or more refills of 60 capsules = 93% of teenagers who returned for a final interview. No significant difference in adherence rates between the groups, so results were not presented separately for adherers and non‐adherers.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	"randomly assigned" ‐ not further described.
Allocation concealment (selection bias)	Low risk	Third party (dispensed by clinic pharmacy).
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Capsules were identical in composition and indistinguishable in taste and appearance, and the code was not broken until the end of the study.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Not reported but likely to have been blinded due to the use of a placebo.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Birthweight data not available for 31/138 (22%); due to 2 spontaneous abortions and 29 records that could not be located.
Selective reporting (reporting bias)	High risk	Data for outcomes such as perinatal death and preterm birth were collected but not fully reported (only that no significant differences were found).
Other bias	Low risk	No apparent source of other bias.