One-Hour Oral Glucose Tolerance Test for the Postpartum Reclassification of Women With Hyperglycemia in Pregnancy
Ravi Retnakaran, Chang Ye, Caroline K. Kramer, Anthony J. Hanley, Philip W. Connelly, Mathew Sermer, Bernard Zinman
Abstract
OBJECTIVE: The International Diabetes Federation recently endorsed a 1-h oral glucose tolerance test (OGTT) as more convenient than the conventional 2-h OGTT. In practice, women with hyperglycemia in pregnancy are advised to undergo a 2-h OGTT within 6 months after delivery, but this test is often not completed, partly owing to its inconvenience for busy mothers. Recognizing the potential advantage of the 1-h OGTT in this setting, we sought to compare 1-h and 2-h OGTT glucose measurements at 3 months postpartum as predictors of dysglycemia (prediabetes/diabetes) over the first 5 years postpartum. RESEARCH DESIGN AND METHODS: A total of 369 women across a range of glucose tolerance in pregnancy (from normoglycemia to gestational diabetes [GDM]) underwent multisample 2-h 75-g OGTTs at 3 months, 1 year, 3 years, and 5 years postpartum. Glucose measurements from the 3-month OGTT were ranked as predictors of dysglycemia (both criteria) by change in concordance index (CCI) of Cox proportional hazard regression models. RESULTS: At the 3-month OGTT, 1-h glucose identified all but 10 of 70 women concurrently diagnosed with dysglycemia by 2-h glucose, while diagnosing an additional 96 women. The cumulative incidence of dysglycemia progressively increased over 5 years by tertile of 1-h glucose on the 3-month OGTT (P < 0.0001). On regression analyses, the strongest predictor of dysglycemia was 1-h glucose (change in CCI: 16.1%), followed by 2-h glucose (14.9%). In women with GDM, 1-h glucose again emerged as strongest predictor of dysglycemia (13.0%), followed by 2-h glucose (12.8%). CONCLUSIONS: The 1-h OGTT may offer a strategy for increasing rates of postpartum reclassification following hyperglycemia in pregnancy.