Gestational diabetes is one of the most common complications during pregnancy. Its incidence has increased in recent decades. This is partly due to improved screening strategies and more stringent diagnostic criteria. Using the updated diagnostic thresholds, it is expected that 5-10% at least of all pregnant women will be diagnosed with diabetes mellitus. The rationale for the novel blood glucose criteria are data from prospective studies reporting an increase of fetal and maternal complications even when the blood glucose is only slightly increased. For the first time, solid evidence now exists for the diagnosis and treatment of gestational diabetes.