Gestational diabetes mellitus (GDM) is defined as carbohydrate intolerance that begins or is first recognized during pregnancy. Although it is a well-known cause of pregnancy complications, a systematic review of its epidemiology has become more complex following the introduction of new World Health Organization /International Association Diabetes in Pregnancy Study Group international criteria. That is for the first time based on the risk of adverse perinatal outcomes. The traditional and most often reported risk factors for GDM are high maternal age, weight and parity, previous delivery of a macrosomic infant, and a family history of diabetes. The number of fetuses in multifetal pregnancies is expected to influence the incidence of GDM owing to the increased placental mass and, thereby, the increase in diabetogenic hormones. Animal studies have shown that female fetuses exposed to a diabetic intrauterine milieu have an increased risk of subsequent GDM.