[Gestational diabetes mellitus (Update 2019)]

Gestational diabetes mellitus (GDM) is defined as a glucose tolerance disorder with onset during pregnancy and is associated with increased feto-maternal morbidity as well as long-term complications in mother and child. Women who fulfil the criteria of a manifest diabetes in early pregnancy (fasting plasma glucose >126 mg/dl, spontaneous glucose level >200 mg/dl or HbA1c > 6.5% before 20 weeks of gestation) should be classified as having manifest diabetes in pregnancy and treated as such. Screening for undiagnosed type 2 diabetes at the first prenatal visit (evidence level B) is particularly recommended in women at increased risk (history of GDM or prediabetes, malformation, stillbirth, successive abortions or birth weight >4500 g in previous pregnancies, obesity, metabolic syndrome, age >35 years, vascular disease, clinical symptoms of diabetes, e. g. glucosuria, or ethnic groups with increased risk for GDM/T2DM, e.g. Arabian countries, south and southeast Asia and Latin America). A GDM is diagnosed by an oral glucose tolerance test (OGTT) or a fasting glucose concentration ≥92 mg/dl. Performance of the OGTT (120 min, 75 g glucose) may already be indicated in the first trimester in high risk women but is mandatory between 24-28 gestational weeks in all pregnant women with previous non-pathological glucose metabolism (evidence level B). Based on the results of the Hyperglycemia and Adverse Pregnancy Outcome (HAPO) study and following the recent WHO recommendations, GDM is present if the fasting plasma glucose level exceeds 92 mg/dl, the 1 h level exceeds 180 mg/dl or the 2 h level exceeds 153 mg/dl after glucose loading (OGTT international consensus criteria). A single increased value is sufficient for the diagnosis and a strict metabolic control is mandatory. After bariatric surgery an OGTT is not recommended due to the risk of postprandial hypoglycemia. All women with GDM should receive nutritional counselling, be instructed in self-monitoring of blood glucose and to increase physical activity to moderate intensity levels, if not contraindicated. If blood glucose levels cannot be maintained in the therapeutic range (fasting <95 mg/dl and 1 h postprandial <140 mg/dl) insulin therapy should be initiated as first choice. 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 re-evaluated by a 75 g OGTT (WHO criteria) 4-12 weeks postpartum to reclassify the glucose tolerance and every 2 years in cases of normal glucose tolerance (evidence level B). All women have to be informed about their (sevenfold increased relative) risk of developing type 2 diabetes (T2DM) at follow-up and possible preventive measures, in particular weight management, healthy diet and maintenance/increase of physical activity. Monitoring of the development of children and recommendations for a healthy lifestyle are necessary for the whole family. Regular obstetric examinations including ultrasound examinations are recommended. Within the framework of neonatal care, neonates of GDM mothers should undergo blood glucose measurements and if necessary appropriate measures should be initiated.