The link between diabetes and poor pregnancy outcomes is well established. As in the non-pregnant population, pregnant women with diabetes can experience profound effects on multiple maternal organ systems. In the fetus, morbidities arising from exposure to diabetes in utero include not only increased congenital anomalies, fetal overgrowth, and stillbirth, but metabolic abnormalities that appear to carry on into early life, adolescence, and beyond. This article emphasizes the newest guidelines for diabetes screening in pregnancy while reviewing their potential impact on maternal and neonatal complications that arise in the setting of hyperglycemia in pregnancy.