β-Cell Function Declines Within the First Year Postpartum in Women With Recent Glucose Intolerance in Pregnancy

OBJECTIVE Both gestational diabetes mellitus (GDM) and mild glucose intolerance in pregnancy identify women at increased risk of future type 2 diabetes. In this context, we queried whether metabolic changes that occur in the 1st year postpartum vary in relation to gestational glucose tolerance status. RESEARCH DESIGN AND METHODS Three-hundred-and-ninety-two women underwent glucose challenge test (GCT) and oral glucose tolerance test (OGTT) in pregnancy followed by repeat OGTT at both 3 months' postpartum and 12 months' postpartum. The antepartum testing defined four gestational glucose tolerance groups: GDM (n = 107); gestational impaired glucose tolerance (GIGT) (n = 75); abnormal GCT with normal glucose tolerance (NGT) on OGTT (abnormal GCT NGT) (n = 137); and normal GCT with NGT on OGTT (normal GCT NGT) (n = 73). RESULTS The prevalence of dysglycemia progressively increased across the groups from normal GCT NGT to abnormal GCT NGT to GIGT to GDM at both 3 months' postpartum (2.7% to 10.2% to 18.7% to 34.6%, P < 0.0001) and 12 months' postpartum (2.7% to 11.7% to 17.3% to 32.7%, P < 0.0001). Between 3 and 12 months' postpartum, the groups did not differ with respect to changes in waist circumference, weight, or insulin sensitivity. Importantly, however, they exhibited markedly different changes in beta-cell function (Insulin Secretion-Sensitivity Index-2 [ISSI-2]) (P = 0.0036), with ISSI-2 declining in both the GDM and GIGT groups. Furthermore, on multiple linear regression analysis, both GDM (t = -3.06, P = 0.0024) and GIGT = -2.18, P = 0.03) emerged as independent negative predictors of the change in ISSI-2 between 3 and 12 months' postpartum. CONCLUSIONS Women with GDM and GIGT exhibit declining beta-cell function in the 1st year postpartum that likely contributes to their future diabetic risk.