Changes in pancreatic B cell function during late pregnancy, early lactation and postlactation.

Oral glucose tolerance tests were performed in 10 normal women during late pregnancy (36 +/- 1 weeks of gestation), early lactation (5 days after delivery) and postlactation (1 week after weaning). A marked decrease in basal plasma insulin and C peptide concentrations, as well as in the B cell secretory response to hyperglycemia, was observed at the 5th day of postpartum, compared to the high values recorded in late pregnancy. Except for a higher basal C peptide level and a lower plasma prolactin concentration, there was no major difference between early lactation and postlactation. At the 5th day after delivery, the insulin response to hyperglycemia was lower in lactating than in nonlactating women (14 subjects in each group). It is concluded that, in normal women, pancreatic B cell function undergoes a rapid normalization during the postpartum, at least when the latter coincides with the onset of lactation.