Effects of new criteria for type 2 diabetes on the rate of postpartum glucose intolerance in women with gestational diabetes.

OBJECTIVE: Our purpose was to determine the impact of the 1997 American Diabetes Association diagnostic criteria for type 2 diabetes mellitus on the rate of postpartum glucose intolerance in women with gestational diabetes. STUDY DESIGN: Women identified as having gestational diabetes were instructed to undergo a 75-g, 2-hour glucose tolerance test 4 to 6 weeks after delivery. The results were retrospectively categorized with both the 1979 National Diabetes Data Group criteria and those recommended by the American Diabetes Association in 1997. RESULTS: Though the rate of overt diabetes mellitus did not increase when the 1997 American Diabetes Association criteria were used (7.8% vs 5.6%, P = not significant), the rate of impaired glucose metabolism was higher (20.1% vs 5%, P <.001). Most women (28/30, 93%) with a nondiagnostic glucose tolerance test result by the older criteria had abnormal results by the newer criteria. Fifty women had abnormalities of glucose metabolism under 1997 American Diabetes Association criteria; 34% of these women had fasting plasma glucose values in the normal range. Of the 25 women with impaired glucose tolerance, 16 (64%) had only an abnormal 2-hour value, with normal fasting glucose values. CONCLUSIONS: The rate of postpartum abnormalities in glucose metabolism more than doubles when the 1997 American Diabetes Association criteria are applied; more women are identified with lesser degrees of impairment. However, relying on fasting glucose levels alone, without glucose tolerance testing, may miss one third of women with such abnormalities.