The clinical usefulness of glucose tolerance testing in gestational diabetes to predict early postpartum diabetes mellitus.

We examined the clinical usefulness of antepartum clinical characteristics, along with measures of glucose tolerance, in Dutch multiethnic women with gestational diabetes mellitus (GDM) for their ability to predict type 2 diabetes within 6 months of delivery (early postpartum diabetes). The present study comprised a cross-sectional 5-year investigation (1998-2003) of a consecutive series of 168 women with GDM identified by a two-stage protocol at 16-33 weeks of gestation. The following data were collected for all women: age and gestational age at entry into the study; prepregnancy body mass index (BMI); ethnicity; obstetric and clinical history, including the onset of early postpartum diabetes; pregnancy outcome; level of fasting C-peptide; and glycemic parameters of 50-g 1-h glucose challenge test and 100-g 3-h oral glucose tolerance test (diagnostic OGTT). We used receiver operating characteristic (ROC) curve analysis to test the clinical usefulness of the glycemic parameters. A total of 11 women (6.5%) developed early postpartum diabetes. Apart from family history of diabetes (p = 0.052), anthropometric, maternal, and neonatal clinical parameters showed no association with early postpartum diabetes in univariate analyses. The level of fasting glucose, and both the glucose challenge test and diagnostic OGTT post-load glucose levels and glucose areas were associated with early postpartum diabetes. ROC curve analysis identifiedall three glucose challenge-test parameters, including fasting glucose concentration, as poor diagnostic tests, with a positive predictive value of approximately 22%, whereas the positive predictive value associated with the area under the diagnostic OGTT curve increased progressively over monitoring time from 20.6% to 100%. Using a 3-h OGTT glucose area threshold of 35.7 mmol.h/L resulted in 100% sensitivity and 100% specificity, identifying the 11 women who developed early postpartum diabetes. In summary, we can conclude from the present analysis that early postpartum diabetes is rare in GDM women (6.5%), and that the clinical usefulness of the total area under the diagnostic 3-h OGTT is superior to all other glycemic parameters for detecting early postpartum diabetes.