Heterogeneous Contribution of Insulin Sensitivity and Secretion Defects to Gestational Diabetes Mellitus

OBJECTIVE: To characterize physiologic subtypes of gestational diabetes mellitus (GDM). RESEARCH DESIGN AND METHODS: Insulin sensitivity and secretion were estimated in 809 women at 24-30 weeks' gestation, using oral glucose tolerance test-based indices. In women with GDM (8.3%), defects in insulin sensitivity or secretion were defined below the 25th percentile in women with normal glucose tolerance (NGT). GDM subtypes were defined based on the defect(s) present. RESULTS: Relative to women with NGT, women with predominant insulin sensitivity defects (51% of GDM) had higher BMI and fasting glucose, larger infants (birth weight z score 0.57 -0.01 to 1.37 vs. 0.03 -0.53 to 0.52, P = 0.001), and greater risk of GDM-associated adverse outcomes (57.6 vs. 28.2%, P = 0.003); differences were independent of BMI. Women with predominant insulin secretion defects (30% of GDM) had BMI, fasting glucose, infant birth weights, and risk of adverse outcomes similar to those in women with NGT. CONCLUSIONS: Heterogeneity of physiologic processes underlying hyperglycemia exists among women with GDM. GDM with impaired insulin sensitivity confers a greater risk of adverse outcomes.