Influence of mineral and vitamin supplements on pregnancy outcome.

The literature was searched for publications on minerals and vitamins during pregnancy and the possible influence of supplements on pregnancy outcome. Maternal iron (Fe) deficiency has a direct impact on neonatal Fe stores and birth weight, and may cause cognitive and behavioural problems in childhood. Fe supplementation is recommended to low-income pregnant women, to pregnant women in developing countries, and in documented deficiency, but overtreatment should be avoided. Calcium (Ca) deficiency is associated with pre-eclampsia and intra-uterine growth restriction. Supplementation may reduce both the risk of low birth weight and the severity of pre-eclampsia. Gestational magnesium (Mg) deficiency may cause hematological and teratogenic damage. A Cochrane review showed a significant low birth weight risk reduction in Mg supplemented individuals. Intake of cereal-based diets rich in phytate, high intakes of supplemental Fe, or any gastrointestinal disease, may interfere with zinc (Zn) absorption. Zn deficiency in pregnant animals may limit fetal growth. Supplemental Zn may be prudent for women with poor gastrointestinal function, and in Zn deficient women, increasing birth weight and head circumference, but no evidence was found for beneficial effects of general Zn supplementation during pregnancy. Selenium (Se) is an antioxidant supporting humoral and cell-mediated immunity. Low Se status is associated with recurrent abortion, pre-eclampsia and IUGR, and although beneficial effects are suggested there is no evidence-based recommendation for supplementation. An average of 20-30% of pregnant women suffer from any vitamin deficiency, and without prophylaxis, about 75% of these would show a deficit of at least one vitamin. Vitamin B6 deficiency is associated with pre-eclampsia, gestational carbohydrate intolerance, hyperemesis gravidarum, and neurologic disease of infants. About 25% of pregnant women in India are folate deficient. Folate deficiency may lead to congenital malformations (neural tube damage, orofacial clefts, cardiac anomalies), anaemia and spontaneous abortions, and pre-eclampsia, IUGR and abruption placentae. Pregestational supplementation of folate prevents neural tube defects. A daily supplemental dose of 400 μg/day of folate is recommended when planning pregnancy. In developing countries diets are generally low in animal products and consequently in vitamin B12 content. An insufficient supply may cause reduced fetal growth. In vegetarian women, supplementation of vitamin B12 may be needed. Vitamin A deficiency is prevalent in the developing world, impairing Fe status and resistance to infections. The recommended upper limit for retinol supplements is 3000 IU/day. Vitamin A supplementation enhances birth weight and growth in infants born to HIV-infected women. Overdosing should be avoided. Low concentrations of vitamin C seem to increase the development of pre-eclampsia, and supplementation may be beneficial. Supplementation with vitamin D in the third trimester in vitamin D deficient women seems to be beneficial. The use of vitamins E, although generally considered "healthy", may be harmful to the pregnancy outcome by disrupting a physiologic oxidative gestational state and is consequently not recommended to prevent pre-eclampsia. Further studies on specific substances are needed as the basis for stratified, placebo-controlled analyses.