Gastrointestinal transit time in human pregnancy: prolongation in the second and third trimesters followed by postpartum normalization.

Fifty-nine studies of gastrointestinal transit time were performed in 27 healthy women during pregnancy and postpartum. Gastrointestinal transit time was defined as the time of the first sustained rise in breath hydrogen concentration after ingestion of 10 g of lactulose. Gastrointestinal transit time was significantly prolonged in both the second and third trimesters of pregnancy (125 +/- 48 min and 137 +/- 58 min, respectively) when compared with either the first trimester of pregnancy or the postpartum period (99 +/- 39 min and 75 +/- 33 min, respectively). Transit times measured in the first trimester were not significantly different from those postpartum. Because the prolongation of transit time in late pregnancy is transient, it is probably due to hormones (perhaps progesterone) or other metabolic effects of pregnancy.