Maternal mineral and vitamin supplementation in pregnancy

Deficiency of vitamins and minerals, collectively known as micronutrients, during pregnancy can have important adverse effects on maternal and birth outcomes. Evidence-based nutrition interventions can make a difference and potentially avert these outcomes. Iron supplementation has been shown to improve maternal mean hemoglobin concentration at term and reduce the risk of anemia. Zinc supplementation has been shown to result in a small but significant reduction in preterm births. A cluster-randomized study in Nepal showed a 40% reduction in maternal mortality up to 12 weeks postpartum with weekly vitamin A and 49% biweekly-carotene supplementation but subsequent large studies in Bangladesh and Ghana have failed to demonstrate any impact on mortality. Maternal vitamin A supplementation has no role in preventing mother-to-child transmission of HIV in HIV-infected pregnant women. Periconceptional folic acid supplementation reduces the risk of neural tube defects, while supplementation with vitamin D reduces the incidence of neonatal hypocalcemia with no impact on craniotabes. Iodine supplementation during pregnancy has also been suggested to reduce the risk of perinatal and infant mortality, and the risk of endemic cretinism at 4 years of age. Calcium supplementation reduced the risk of preeclampsia in women with low baseline calcium dietary intake, while magnesium supplementation has been associated with a lower frequency of preterm births and adverse neurodevelopmental outcomes in childhood. Other vitamins and minerals, such as vitamins B, C and E, copper and selenium, have been associated with fetal development, but their impact on pregnancy outcomes is not clear. Given such widespread maternal vitamin and mineral deficiencies, it is logical to consider supplementation with multiple micronutrient preparations in pregnancy. The clinical benefits of such an approach over single-nutrient supplements are unclear, and this article explores the current concepts, evidence and limitations of maternal multiple-micronutrient supplementation.