Advances in Gestational Diabetes Mellitus

Gestational diabetes mellitus (GDM) develops during pregnancy in women whose pancreatic function is insufficient to overcome the insulin resistance associated with the pregnant state. For many years, GDM was defined as any degree of glucose intolerance that was first recognized during pregnancy. The ongoing epidemic of obesity and diabetes has led to more type 2 diabetes in women of childbearing age, with an increase in the number of pregnant women with undiagnosed type 2 diabetes. Therefore the definition of GDM is modified to diabetes that is first diagnosed in the 2nd or 3rd trimester of pregnancy that is not clearly either preexisting type 1 or type 2 diabetes.The prevalence of GDM as traditionally defined is approximately 6 percent of pregnant women in the United States. The prevalence varies worldwide because of differences in screening practices, population characteristics (e.g. average age and body mass index [BMI] of pregnant women), testing method, and diagnostic criteria. Women at low risk of GDM are young (<25 years of age), non-Hispanic white, with normal BMI (<25 kg/m2), no history of previous glucose intolerance or adverse pregnancy outcomes associated with GDM, and no first-degree relative with diabetes. Only 10 percent of the general obstetric population meets all of these criteria for low risk of developing GDM, which is the basis for universal rather than selective screening. The main consequences of GDM are increased risks of preeclampsia, macrosomia, and cesarean delivery, and their associated morbidities. The risks of these outcomes increase as maternal fasting plasma glucose levels increase above 75 mg/dL and as the 1-hr and 2-hr oral GTT values.Most women with GDM can achieve normoglycemia with nutritional therapy alone. Exercise that increases muscle mass appears to improve glycemic control primarily from increased tissue sensitivity to insulin and, in some women with GDM, the need for insulin may be obviated. Insulin therapy has been the well-studied and used treatment. Most professional societies recommend insulin as first-line treatment of GDM after failure of lifestyle modification. Commonly used oral hypoglycemic agents are glyburide and metformin. Both cross the placenta and long-term safety data is limited. Current literatures suggest that metformin may reduce several common shortterm adverse outcomes related to GDM.