(1046) Disposition Index as a Predictor of Diabetes Development in Women with Gestational Diabetes

Objective:
Gestational diabetes mellitus (GDM) increases the risk of developing type 2 diabetes mellitus (DM) postpartum. The disposition index (DI), reflecting pancreatic beta-cell function in response to insulin resistance, is a potent predictor of diabetes development outside pregnancy. This study aimed to evaluate the utility of early postnatal DI in predicting DM development within three years postpartum in women with GDM.

Study Design:
This prospective cohort study included singleton pregnant Japanese women diagnosed with GDM during pregnancy. An oral glucose tolerance test (OGTT) was conducted at 6 to 9 weeks postpartum and repeated every 6 to 12 months. The primary outcome was the development of DM within three years postpartum. Using early postpartum OGTT results, we calculated the Matsuda index (MI) and AUCins/AUCglu (area under the curve of insulin/glucose) over 120 minutes as indices of insulin sensitivity and secretion, respectively, and DI (MI x AUCins/AUCglu). We examined the association between DI and DM development, adjusting for potential confounders including age, family history of DM, insulin treatment during pregnancy, obesity, and breastfeeding.

Results:
Among 363 women with GDM (mean age 34 ± 5 years, prepregnancy BMI 23.7 ± 5.0), 14 developed DM (3.9%). DI was significantly lower in the DM group compared to the non-DM group (1.17 ± 0.30 vs. 1.83 ± 0.65, p < 0.01). A low DI was significantly associated with DM development (Figure). Women with a DI less than 1.58, derived from the receiver operating characteristic curve, had significantly higher odds of developing DM (crude odds ratio 20.6, adjusted odds ratio 12.5; 95% confidence intervals 4.0-376.3 and 2.3-234.6, respectively). Neither MI nor AUCins/AUCglu was significantly associated with DM development.

Conclusion:
In Japanese women with GDM, early postnatal DI is a significant predictor of DM development within three years postpartum. Women who developed DM already had impaired beta-cell response to insulin resistance during the early postpartum period.