Effect of gestational zinc deficiency on pregnancy outcomes: summary of observation studies and zinc supplementation trials.

The lack of a valid indicator precludes a true estimate of zinc deficiency in pregnancy in various populations. However, it is possible that mild to moderate deficiency (as assessed by available indicators) may be common in the developing world. Animal experiments indicate that zinc deficiency can result in adverse maternal and fetal consequences. Human data, particularly from prenatal zinc supplementation trials, has failed to document a consistent maternal or infant benefit on evaluated outcome measures including pregnancy induced hypertension, preterm/post-term labour, premature rupture of membranes, maternal infection, postpartum haemorrhage, perinatal mortality, congenital malformations and fetal growth and gestation. Preliminary data suggest a beneficial effect of prenatal zinc supplementation on infants' neurobehavioural development and immune function (evaluated by diarrhoeal and ARI morbidity incidence in the first year of life). Future research should focus on these functional consequences and congenital malformations (with adequate sample sizes), and simultaneously address the safety issue, particularly in relation to micronutrient interactions. In the light of the currently available information, routine zinc supplementation can not be advocated to improve pregnancy outcome.