| Methods |
A double‐blind, RCT. |
| Participants |
213 Hispanic women of Mexican descent 17 years of age or older who were not over 27 weeks of gestational age. They were without diabetes or heart, renal or thyroid disease were selected for study. Women specifically selected on the basis of being at high risk for low zinc status ‐ at baseline, 81% of women had recalled dietary intakes providing < 2/3 RDA. 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 obtain information from their clinic, delivery, and infant records. |
| Interventions |
Women were randomly assigned into 2 groups. The treatment group received a daily vitamin and mineral supplement as a single capsule providing about 20 mg of zinc as zinc acetate. The control group received a similar supplement without zinc. The capsules were indistinguishable in appearance. The capsule bottles
were labelled A or B (Balancel Forte, Meyer Laboratories, Ft Lauderdale, FL). Meyer Laboratory provided the supervisor of the clinic pharmacy with the information necessary to identify the capsules containing zinc. The women were instructed to take the capsule with their evening meal to reduce the possible transitory effect on zinc concentrations in serum samples which were collected in the morning. All supplements were formulated to provide 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 HCI, 1 mg folic acid, 10 µg vitamin B12 (cyanocobalamin), 10 mg D‐calcium pantothenate, 60 mg vitamin C, 100 mg calcium (as carbon ate), 20 mg iron (as ferrous fumarate), 50 mg of magnesium (as oxide), 1 mg of manganese (as sulphate), and 150 µg iodine (as potassium iodide) per day.
Zinc: 20 mg elemental zinc plus vitamins (n = 107).
Placebo with vitamins: (n = 106).
|
| Outcomes |
Pregnancy hypertension;
low serum zinc before. birth (< 53.3 µg/dL;
low hair zinc;
smell dysfunction;
taste dysfunction;
preterm birth;
low birthweight. |
| Notes |
Adherence: defined as a woman who was in the study long enough to take supplements for more than 60 days and who returned to the pharmacy for 1 or more refills of 60 capsules. According to this definition, 82% overall (90% (81/90) in the control group and 75% (65/87) in the zinc group) were adherent in those 177 women who were not lost to follow‐up. |
| Risk of bias |
| Bias |
Authors' judgement |
Support for judgement |
| Random sequence generation (selection bias) |
Unclear risk |
Method of sequence generation not reported. |
| Allocation concealment (selection bias) |
Low risk |
"randomly assigned" ‐ not definitively stated but likely to have been third party randomisation. |
| Blinding of participants and personnel (performance bias)
All outcomes |
Low risk |
"double‐blind"; "capsules were indistinguishable." |
| Blinding of outcome assessment (detection bias)
All outcomes |
Unclear risk |
Not reported but stated that "code was not broken until the study was completed". |
| Incomplete outcome data (attrition bias)
All outcomes |
Unclear risk |
36/213 (16.9%) lost to follow‐up (3 spontaneous abortions < 20 weeks, 2 sets of twins, 31 records that could not be located). The breakdown was 20/107 (18.7%) lost from the zinc group and 16/106 (15.1%) from the placebo group. Breakdown of reasons was not reported except for spontaneous abortions ‐ 1 in the zinc group and 2 in the control group. |
| Selective reporting (reporting bias) |
Unclear risk |
A number of primary maternal, pregnancy and neonatal outcomes were not reported (e.g. caesarean section, postpartum haemorrhage, perinatal death). |
| Other bias |
Low risk |
No apparent source of other bias. |
