A number of challenges remain for screening and diagnostic testing for GDM. All of the diagnostic criteria for pregnancy in common use in the United States are based on the 100-g, 3-hour Oral Glucose Tolerance Test (OGTT). There are a number of reasons, however, that a 75-g test would be preferable. First, when a glucose tolerance test is administered to nonpregnant individuals, it is standard to use the 75-g, 2-hour OGTT. Using a different glucose challenge in pregnant verses nonpregnant patients leads to confusion in the laboratory and may result in errors in applying the proper diagnostic criteria. Further, the 75-g, 2-hour OGTT is in use during pregnancy in many countries around the world, typically using the same thresholds as in nonpregnant individuals. Development and validation of pregnancy-based criteria using the 75-g, 2-hour OGTT would simplify world wide comparison of data and the testing paradigm used in the United States.
Coustan, Donald R. MD, “Making the diagnosis of Gestational Diabetes Mellitus (Diabetes and Pregnancy)” Clin Obstet Gynecol. 2000 Mar;43(1):99-105.