Screening and diagnosis of gestational diabetes has lacked uniform criteria both nationally and internationally. In addition, the relationship between the degree of hyperglycemia or glucose intolerance and the risk of maternal, fetal, and neonatal adverse outcomes has not been clearly established. The International Association of Diabetes and Pregnancy Study Groups (IADPSG) recently published their recommendation for diagnosing and classifying gestational hyperglycemia in pregnancy after evaluation of the results of the Hyperglycemia and Adverse Pregnancy Outcome (HAPO) observational study. Their recommendations have recently been accepted by the American Diabetes Association and are currently under review by the American College of Obstetricians and Gynecologist (ACOG) in the United States. If accepted in the United States and internationally, the world would have consistent thresholds for evaluating hyperglycemia in pregnancy, which would not only include the diagnosis of gestational diabetes mellitus but also overt diabetes, which has not been encompassed by previously accepted definitions.