Micronutrients and reproductive health issues: an international perspective.

Micronutrients may have a role in enhancing reproductive health of women living in the developing world. Two illustrative micronutrients, zinc and vitamin A, have received some attention in this regard. Numerous animal experiments and observational studies suggest the potential role of zinc deficiency in labor and delivery-related complications such as premature rupture of membrane, placental abruption, preterm labor and inefficient uterine contraction. These associations have not been confirmed in supplementation studies. Zinc does not appear to be a limiting factor in intrauterine growth in the developing world, contrary to some evidence of its suggested benefit among women residing in industrialized countries. One study in Nepal found that maternal vitamin A or beta-carotene supplementation reduces pregnancy-related mortality but not infant mortality. These findings are corroborated by observations of the significantly higher risk of mortality among night-blind women compared to non-night-blind women long after the termination of pregnancy and the resolution of night blindness. Maternal multiple micronutrient supplementation needs more careful evaluation before its use in large-scale programs. Two recent trials indicated that a prenatal multiple micronutrient supplement provides no added advantage over iron and folate in reducing outcomes such as low birth weight and probably no survival benefit. Data are also suggestive that adding zinc may negate the beneficial effect of iron and folic acid on birth weight. Research is needed to further our understanding of nutrient-nutrient interactions.