Gestational diabetes mellitus (GDM)9 is a common disorder of pregnancy associated with increased risks for the mother [obstructed labor and later type 2 diabetes mellitus (T2DM)] and baby (congenital malformations, macrosomia, and neonatal hypoglycemia). Offspring of mothers with GDM have an increased risk of developing adult obesity and T2DM (1). Risk factors for GDM are similar to those for T2DM (older age and greater adiposity) and the prevalence is rising everywhere (2). The Hyperglycemia and Adverse Pregnancy Outcomes study showed that the complications of GDM increase linearly across the range of plasma glucose values, leading to debate about the best clinical criteria for diagnosing GDM (3, 4).