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 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.Thomas R Moore, MD et al. Diabetes Mellitus and Pregnancy. . Version: Jan 27, 2005 update. No specific cause has been identified, but it is believed that the hormones produced during pregnancy increase a woman's resistance to insulin, 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 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.

Definition

Gestational diabetes is formally defined as "any degree of glucose intolerance with onset or first recognition during pregnancy".Metzger BE, Coustan DR (Eds.). Proceedings of the Fourth International Work-shop-Conference on Gestational Diabetes Mellitus. Diabetes Care 1998; 21 (Suppl. 2): B1–B167. This definition acknowledges the possibility that patients may have previously undiagnosed diabetes mellitus, or may have developed diabetes coincidentally with pregnancy. Whether symptoms subside after pregnancy is also irrelevant to the diagnosis .American Diabetes Association. Gestational Diabetes Mellitus. Diabetes Care 2004; 27: S88-90. PMID 14693936

Epidemiology

The frequency of gestational diabetes varies widely by study depending on the population studied and the study design. It occurs in between 5 and 10% of all pregnancies (between 1-14% in various studies).

Pathophysiology

The precise mechanisms underlying gestational diabetes remain unknown. The hallmark of GDM is increased insulin resistance. Pregnancy hormones and other factors are thought to interfere with the action of insulin as it binds to the insulin receptor. The interference probably occurs at the level of the cell signaling pathway behind the insulin receptor.Carr DB, Gabbe S. Gestational Diabetes: Detection, Management, and Implications. Clin Diabetes 1998; 16(1): 4.. Since insulin promotes the entry of glucose into most cells, insulin resistance prevents glucose from entering the cells properly. As a result, glucose remains in the bloodstream, where glucose levels rise. More insulin is needed to overcome this resistance; about 1.5-2.5 times more insulin is produced in a normal pregnancy.Carr DB, Gabbe S. Gestational Diabetes: Detection, Management, and Implications. Clin Diabetes 1998; 16(1): 4.