Protein turnover in pregnancy.

Whole-body protein metabolism was studied at 13, 24 and 35 weeks gestation in six healthy women using a continuous infusion [13C]leucine technique. Values were expressed in terms of fat-free body weight (FFM) calculated using literature standards for changes in total body potassium during pregnancy. Mean protein synthesis increased from 5.3 (+/- 0.6 SD) g/kg FFM/24h at 13 weeks to 5.9 +/- 0.5 (P less than 0.1) at 24 weeks and 6.1 +/- 0.6 at 35 weeks (P less than 0.05 vs 3 weeks). Similar increases were noted in catabolism so that net loss changed little. Protein synthesis at 24 and 35 weeks gestations was significantly greater than that in 17 healthy, non-pregnant women (4.9 +/- 0.6, P less than 0.001). These data indicate that there are substantial increases in protein turnover during pregnancy.