Gestational diabetes: antepartum characteristics that predict postpartum glucose intolerance and type 2 diabetes in Latino women

Abstract

We examined antepartum clinical characteristics along with measures of glucose tolerance, insulin sensitivity, pancreatic beta-cell function, and body composition in Latino women with gestational diabetes mellitus (GDM) for their ability to predict type 2 diabetes or impaired glucose tolerance (IGT) within 6 months after delivery. A total of 122 islet cell antibody-negative women underwent oral and intravenous glucose tolerance tests (OGTT; IVGTT), hyperinsulinemic-euglycemic clamps, and measurement of body fat between 29 and 36 weeks' gestation and returned between 1 and 6 months postpartum for a 75-g OGTT. Logistic regression analysis was used to examine the relationship between antepartum variables and glucose tolerance status postpartum. At postpartum testing, 40% of the cohort had normal glucose tolerance, 50% had IGT, and 10% had diabetes by American Diabetes Association criteria. Independent antepartum predictors of postpartum diabetes were the 30-min incremental insulin:glucose ratio during a 75-g OGTT (P = 0.0002) and the total area under the diagnostic 100-g glucose tolerance curve (P = 0.003). Independent predictors of postpartum IGT were a low first-phase IVGTT insulin response (P = 0.0001), a diagnosis of GDM before 22 weeks' gestation (P = 0.003), and weight gain between prepregnancy and the postpartum examination (P = 0.03). All subjects had low insulin sensitivity during late pregnancy, but neither glucose clamp nor minimal model measures of insulin sensitivity in the 3rd trimester were associated with the risk of IGT or diabetes within 6 months' postpartum. These results highlight the importance of pancreatic beta-cell dysfunction, detectable under conditions of marked insulin resistance in late pregnancy, to predict abnormalities of glucose tolerance soon after delivery in pregnancies complicated by GDM. Moreover, the association of postpartum IGT with weight gain and an early gestational age at diagnosis of GDM suggests a role for chronic insulin resistance in mediating hyperglycemia outside the 3rd trimester in women with such a beta-cell defect.