A 100-g oral glucose tolerance test (OGTT) is commonly used to diagnose gestational diabetes
mellitus (GDM). Carpenter–Coustan (CC) criteria, based on lower threshold plasma glucose values than the
National Diabetes Data Group (NDDG) criteria, result in an apparently increased prevalence of GDM. However,
the extent of the increase is not known, and effects on perinatal outcome are not clear