Insulin deficiency is associated with early postpartum T2DM in Indian women with gestational diabetes

Women with gestational diabetes mellitus (GDM) are at increased risk of type 2 diabetes mellitus (T2DM). Understanding the pathophysiology of postpartum T2DM is crucial for prevention. We conducted a prospective study to characterize insulin mechanics in postpartum T2DM among women with GDM.

GDM was diagnosed by oral glucose tolerance test (OGTT) or oral glucose challenge test. We administered an OGTT at 6 weeks and 3, 6, and 12 months postpartum. Postpartum T2DM was defined by the American Diabetes Association criteria at any time point. We assessed whether the insulinogenic index (a measure of early-phase insulin secretion) or the Matsuda index (a measure of insulin sensitivity) at 6 weeks postpartum was associated with T2DM at any time point.

Of 100 women [median age 28 years (IQR 25-32), BMI 27.6 kg/m² (IQR 23.8-30.6) at 6 weeks postpartum], 42% (39) developed T2DM by 1 year postpartum. Among those with T2DM, 67% (26) were diagnosed at 6 weeks postpartum. Age, height, and baseline weight were similar in women with and without T2DM. Baseline triglycerides were higher (127.6 vs. 93.1 mg/dL, p=0.02) among women with T2DM. In proportional hazards analysis, a higher insulinogenic index at 6 weeks postpartum was protective against T2DM [aHR 0.24, 95% CI (0.11, 0.51], independent of age, BMI, triglycerides, and insulin use. The Matsuda index was not associated with T2DM (p=0.53).

Over 40% of women with GDM developed T2DM by 12 months postpartum, most within 6 weeks. Insulin secretion was more strongly associated with T2DM than insulin sensitivity. Earlier screening and further study of the role of beta-cell preservation may help reduce T2DM among young Indian women.