Isocaloric balanced protein supplementation in pregnancy

To assess the effects of providing pregnant women with isocaloric protein supplements (ie where the protein replaces an equal quantity of nonprotein energy) on gestational weight gain and on the outcome of pregnancy.

The register of clinical trials maintained and updated by the Cochrane Pregnancy and Childbirth Group.

All acceptably controlled comparisons of isocaloric protein supplementation, as long as the protein content of the supplement was 'balanced', ie the protein provided <25% of its total energy content.

Data were extracted by the author from published reports, and supplemented by additional information from trialists contacted by the author.

Three trials involving 966 women were included. The results suggest a decrease in maternal weight gain and mean birth weight and an increased risk of small-for-gestational-age (SGA) births with isocaloric protein supplementation, but no effect on mean gestational age or preterm birth. The data are insufficient to exclude potentially important effects on fetal or neonatal mortality, and maternal health outcomes have not been reported.

Balanced protein supplementation alone (ie without energy supplementation) is unlikely to be of benefit to pregnant women or their infants.