Gestational diabetes (or gestational diabetes mellitus, GDM) is a condition in which women without previously diagnosed diabetes exhibit high blood glucose levels during pregnancy (especially during their third trimester). There is some question whether the condition is natural during pregnancy.[citation needed] Gestational diabetes is caused when the insulin receptors do not function properly. This is likely due to pregnancy-related factors such as the presence of human placental lactogen that interferes with susceptible insulin receptors. This in turn causes inappropriately elevated blood sugar levels.

Gestational diabetes generally has few symptoms and it is most commonly diagnosed by screening 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, so may be a natural phenomenon.

As with diabetes mellitus in pregnancy in general, babies born to mothers with untreated gestational diabetes are typically at increased risk of problems such as being large for gestational age (which may lead to delivery complications), low blood sugar, and jaundice. If untreated, it can also cause seizures or stillbirth. Gestational diabetes is a treatable condition and women who have adequate control of glucose levels can effectively decrease these risks. The food plan is often the first recommended target for strategic management of GDM.

Women with unmanaged gestational diabetes are at increased risk of developing type 2 diabetes mellitus (or, very rarely, latent autoimmune diabetes or Type 1)[citation needed] after pregnancy, as well as having a higher incidence of pre-eclampsia and Caesarean section;[3] their offspring are prone to developing childhood obesity,[citation needed] with type 2 diabetes later in life.[citation needed] Most patients are able to manage their blood glucose levels with a modified diet and the introduction of moderate exercise, but some require antidiabetic drugs, including insulin.