Energy and protein intake in pregnancy

Abstract

Gestational weight gain is positively associated with fetal growth, and observational studies of food supplementation in pregnancy have reported increases in gestational weight gain and fetal growth. To assess the effects of advice to increase or reduce energy or protein intake, or of actual energy or protein supplementation or restriction, during pregnancy on energy and protein intakes, gestational weight gain, and the outcome of pregnancy. We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (November 2009) and contacted researchers in the field. Acceptably controlled trials of dietary advice to increase or reduce energy or protein intake, or of actual energy or protein supplementation or restriction, during pregnancy. We extracted data from published reports, supplemented by additional information from the trialists we contacted. In five trials (1135 women), nutritional advice to increase energy and protein intakes was successful in achieving those goals, but no consistent benefit was observed on pregnancy outcomes. In 13 trials (4665 women), balanced energy/protein supplementation was associated with modest increases in maternal weight gain and in mean birthweight, and a substantial reduction in risk of small-for-gestational-age (SGA) birth. These effects did not appear greater in undernourished women. No significant effects were detected on preterm birth, but significantly reduced risks were observed for stillbirth and neonatal death. In two trials (529 women), high-protein supplementation was associated with a small, non-significant increase in maternal weight gain but a non-significant reduction in mean birthweight, a significantly increased risk of SGA birth, and a non-significantly increased risk of neonatal death. In three trials, involving 966 women, isocaloric protein supplementation was also associated with an increased risk of SGA birth. In four trials (457 women), energy/protein restriction of pregnant women who were overweight, or exhibited high weight gain, significantly reduced weekly maternal weight gain and mean birthweight but had no effect on pregnancy-induced hypertension or pre-eclampsia. Dietary advice appears effective in increasing pregnant women's energy and protein intakes but is unlikely to confer major benefits on infant or maternal health. Balanced energy/protein supplementation improves fetal growth and may reduce the risk of fetal and neonatal death. High-protein or balanced-protein supplementation alone is not beneficial and may be harmful to the fetus. Protein/energy restriction of pregnant women who are overweight, or exhibit high weight gain, is unlikely to be beneficial and may be harmful to the fetus.