Postpartum testing for antecedent gestational diabetes.

Gestational diabetes is a predictor of glucose intolerance in subsequent pregnancies and in the nongravid state. Many pregnant women are not tested for gestational diabetes, although they or their offspring may show signs suggestive of antecedent hyperglycemia. We examined the diagnostic utility of a postpartum (within 48 hours), 100 gm, oral glucose tolerance test and cord plasma glucose, cord plasma C-peptide, and 2-hour neonatal plasma glucose tests to detect antecedent gestational diabetes in women with documented gestational diabetes (n = 37) or with normal glucose tolerance test results late in the third trimester (n = 28). The 1-hour, 2-hour, and incremental 1-hour + 2-hour [( 1-hour - fasting] + [2-hour - fasting]) [2-hour - fasting]) glucose values of the postpartum glucose tolerance test showed significant differences between study participants with and without gestational diabetes (164 +/- 30 versus 115 +/- 22, 145 +/- 31 versus 101 +/- 21, and 153 +/- 51 versus 67 +/- 33 mg/dl, respectively, p less than 0.025). Maternal fasting and 3-hour postpartum glucose tolerance test glucose, cord plasma glucose, cord plasma C-peptide, and 2-hour neonatal plasma glucose values showed no significant between-group differences. Receiver operating characteristic curve analyses for these tests indicated that the incremental 1-hour + 2-hour postpartum glucose tolerance test glucose values best sustain test specificity at the low test threshold values necessary for high test sensitivity. A threshold of 110 mg/dl for this test yielded a predicted specificity of 90% and sensitivity of 80% with regard to antecedent gestational diabetes.