Zinc supplementation for improving pregnancy and infant outcome

Mahomed K, Bhutta ZA, Middleton P

Published Online:

August 10, 2011

Taking zinc during pregnancy helps to slightly reduce preterm births, but does not help prevent other problems such as low birthweight babies.

Many women of childbearing age may have mild to moderate zinc deficiency. Low zinc levels may cause preterm birth or they may prolong labour. It is also possible that zinc deficiency may affect infant growth as well. The review of 17 trials, involving over 9000 women and their babies, found that although zinc supplementation has a small effect on reducing preterm births, it does not help to prevent low birthweight babies. Finding ways to improve women's overall nutritional status, particularly in low-income areas, will do more to improve the health of mothers and babies than supplementing pregnant women with zinc.

Abstract (click to read)

Background:

It has been suggested that low serum zinc levels may be associated with suboptimal outcomes of pregnancy such as prolonged labour, atonic postpartum haemorrhage, pregnancy-induced hypertension, preterm labour and post-term pregnancies, although many of these associations have not yet been established.

Objectives:

To assess the effects of zinc supplementation in pregnancy on maternal, fetal, neonatal and infant outcomes.

Search strategy:

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (February 2007). We updated this search on 1 July 2011 and added the results to the awaiting classification section of the review.

Selection criteria:

Randomised or quasi-randomised trials of zinc supplementation in pregnancy.

Data collection and analysis:

Two review authors applied the study selection criteria, assessed trial quality and extracted data. When necessary, study authors were contacted for additional information.

Main results:

We included 17 randomised controlled trials (RCTs) involving over 9000 women and their babies. Zinc supplementation resulted in a small but significant reduction in preterm birth (relative risk (RR) 0.86, 95% confidence interval (CI) 0.76 to 0.98 in 13 RCTs; 6854 women). This was not accompanied by a similar reduction in numbers of babies with low birthweight (RR 1.05 95% CI 0.94 to 1.17; 11 studies of 4941 women). No significant differences were seen between the zinc and no zinc groups for any of the other primary maternal or neonatal outcomes, except for a small effect favouring zinc for caesarean section (four trials with high heterogeneity) and for induction of labour in a single trial. No differing patterns were evident in the subgroups of women with low versus normal zinc and nutrition levels or in women who complied with their treatment versus those who did not.

Authors' conclusions:

The 14% relative reduction in preterm birth for zinc compared with placebo was primarily in the group of studies involving women of low income and this has some relevance in areas of high perinatal mortality. There was no convincing evidence that zinc supplementation during pregnancy results in other useful and important benefits. Since the preterm association could well reflect poor nutrition, studies to address ways of improving the overall nutritional status of populations in impoverished areas, rather than focusing on micronutrient and or zinc supplementation in isolation, should be an urgent priority.

[Note: The 18 citations in the awaiting classification section of the review may alter the conclusions of the review once assessed.]

This record should be cited as:

Mahomed K, Bhutta ZA, Middleton P. Zinc supplementation for improving pregnancy and infant outcome. Cochrane Database of Systematic Reviews 2007, Issue 2. Art. No.: CD000230. DOI: 10.1002/14651858.CD000230.pub3

Assessed as up to date:

February 1, 2007

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Primary Review Group:

Pregnancy and Childbirth Group

Health topics:

Pregnancy & childbirth > Nutrition during pregnancy and postpartum > Vitamins/minerals

Complementary & alternative medicine > Pregnancy & childbirth > Nutrition during pregnancy and postpartum

Cochrane Summaries^beta

Independent high-quality evidence for health care decision making

Zinc supplementation for improving pregnancy and infant outcome

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