Gestational diabetes (or gestational diabetes mellitus, GDM) is a condition in which women without previously diagnosed diabetes exhibit high blood glucose levels during pregnancy.

Gestational diabetes generally has few symptoms and it is most commonly diagnosed byscreening during pregnancy. Diagnostic tests detect inappropriately high levels of glucose in blood samples. Gestational diabetes affects 3-10% of pregnancies, depending on the population studied. No specific cause has been identified, but it is believed that the hormones produced during pregnancy increase a woman's resistance to, resulting in impaired glucose tolerance.

Babies born to mothers with gestational diabetes are at increased risk of problems typically such as being large for gestastional age (which may lead to delivery complications), low blood sugar, and jaundice. Gestational diabetes is a treatable condition and women who have adequate control of glucose levels can effectively decrease these risks.

Women with gestational diabetes are at increased risk of developing type 2 diabetes mellitus (or, very rarely, latent autoimmune diabetes or Type 1) after pregnancy, while their offspring are prone to developing childhood obesity>, with type 2 diabetes later in life. Most patients are treated only with diet modification and moderate exercise but some take anti-diabetic drugs, including insulin.