Gestational diabetes (GDM) is defined as any degree of glucose intolerance with onset or first recognition during pregnancy. GDM is becoming an increasing health problem worldwide and one of the most common complications of pregnancy. The prevalence of GDM in Central Europe is 5-7%. GDM is associated with increased feto-maternal morbidity as well as long-term complications in mothers and offspring. The key symptom of GDM is the development of diabetic fetopathy. Fetal hyperinsulinism is associated with macrosomia and a higher rate of birth injuries and caesarean sections, neonatal hypoglycemia, respiratory distress and due to fetal programming the development of the sequelae of the metabolic syndrome in childhood or adolescence. GDM is commonly diagnosed by an oral glucose tolerance test (OGTT) between gestational weeks 24 and 28. In addition, in case of a high risk of GDM (history of poor obstetric outcome: stillbirth, congenital malformation, birth weight > or = 4500 g or a history of impaired glucose tolerance or impaired fasting glucose) impaired glucose metabolism or diabetes should be excluded in the first trimester. GDM shares the same pathophysiology and clinical signs as diabetes mellitus type 2. Thus maternal obesity, higher age, hypertension as well as a positive family history of type 2 diabetes are high risk factors for the development of GDM. If GDM is diagnosed, a strict metabolic control is mandatory. All women should receive nutritional counseling and be instructed in blood glucose self-monitoring. If blood glucose levels cannot be maintained in the normal range (fasting < 95 mg/dl and 1 h after meals < 130 mg/dl), insulin therapy should be initiated. Maternal and fetal monitoring is required in order to minimize maternal and fetal/neonatal morbidity and perinatal mortality. After delivery, all women with GDM have to be reevaluated as to their glucose tolerance by a 75 gOGTT (WHO criteria). While 85% of these women will return to normal glucose tolerance 8 weeks postpartum, those with persisting impaired glucose tolerance are at particularly high risk for diabetes.