Nutritional interventions during pregnancy for the prevention or treatment of maternal morbidity and preterm delivery: an overview of randomized controlled trials.

This overview assesses the effectiveness of nutritional interventions to prevent or treat maternal morbidity, mortality and preterm delivery. Cochrane systematic reviews and other up-to-date systematic reviews and individual randomized controlled trials were sought. Searches were carried out up to July 2002. Iron and folate supplements reduce anemia and should be included in antenatal care programs. Calcium supplementation to women at high risk of hypertension during pregnancy or low calcium intake reduced the incidence of both preeclampsia and hypertension. Fish oil and vitamins E and C are promising for preventing preeclampsia and preterm delivery and need further testing. Vitamin A and beta-carotene reduced maternal mortality in a large trial; ongoing trials should provide further evaluation. No specific nutrient supplementation was identified for reducing preterm delivery. Nutritional advice, magnesium, fish oil and zinc supplementation appear promising and should be tested alone or together in methodologically sound randomized controlled trials. Anema in pregnancy can be prevented and treated effectively. Considering the multifactorial etiology of the other conditions evaluated, it is unlikely that any specific nutrient on its own, blanket interventions or magic bullets will prevent or treat preeclampsia, hemorrhage, obstructed labor, infections, preterm delivery or death during pregnancy. The few promising interventions for specific outcomes should be tested or reconsidered when results of ongoing trials become available. Until then, women and their families should receive support to improve their diets as a general health rule, which is a basic human right.