Sustained Decrease of Early-Phase Insulin Secretion in Japanese Women with Gestational Diabetes Mellitus Who Developed Impaired Glucose Tolerance and Impaired Fasting Glucose Postpartum.

OBJECTIVE: The aim of this study was to compare glucose intolerance in the antenatal and the postpartum periods using a 75-g oral glucose tolerance test (OGTT) in the Japanese women with gestational diabetes mellitus (GDM) using a retrospective design.

PATIENTS AND METHODS: Data were obtained from 85 Japanese women with GDM who delivered from April 2011 through April 2015 and who underwent an OGTT 6-14 weeks postpartum. The women were divided into two groups based on the results of the postpartum OGTT: one group with normal glucose tolerance (NGT) and the other with impaired glucose tolerance (IGT) as well as impaired fasting glucose (IFG). We analyzed the associations between postpartum IGT-IFG and various factors.

RESULTS: Antenatally, a significant difference was observed between the groups only in the 1-hour plasma glucose level of the 75-g OGTT. Postpartum results of plasma glucose level were significantly higher at 0.5, 1, and 2 hours in the IGT-IFG group than those in the NGT group. Moreover, a significant decrease in the levels of 0.5-hour immunoreactive insulin and insulinogenic index was observed in the IGT-IFG group compared to those in the NGT group. Homeostasis model assessment-insulin resistance and homeostasis model assessment β-cell function of both groups were found to significantly decrease in the postpartum period; however, there was no significant change in the insulinogenic index of either group.

CONCLUSIONS: Our study clearly showed that the postpartum IGT and IFG levels of Japanese women with GDM are affected by impaired early-phase insulin secretion; however, insulin resistance promptly improves.