One-Hour Oral Glucose Tolerance Test for the Postpartum Reclassification of Women With Hyperglycemia in Pregnancy

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.

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.

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%).

The 1-h OGTT may offer a strategy for increasing rates of postpartum reclassification following hyperglycemia in pregnancy.