Gestational diabetes is defined as carbohydrate intolerance of variable severity with onset during the present pregnancy. The definition applies regardless of whether insulin is used for treatment or the condition persists after pregnancy, but it does not exclude the possibility that glucose intolerance may have antedated the pregnancy.

The American College of Obstetricians and Gynecologists recommends that screening for gestational diabetes be done for women with one or more risk factors, including maternal age of 30 years or greater, family history of diabetes, previous macrosomic infant, previous stillbirth, previous malformed infant, obesity, hypertension, or glycosuria. The American Diabetes Association and the Centers for Disease Control and Prevention recommend screening all pregnant women between the twenty-fourth and twenty-eighth gestational week with a 50-g oral glucose challenge. A plasma glucose value of 140 mg per deciliter or greater 1 hour after a 50-g oral glucose dose indicates the need for a full diagnostic glucose tolerance test. It does not, by itself, establish the diagnosis. Diagnosis is based on results of the 100-g oral glucose tolerance test, interpreted according to the diagnostic criteria of O’Sullivan and Mahan (

Table 372-1).

All patients with gestational diabetes are at significant risk for fetal macrosomia with consequent birth trauma, as well as other neonatal complications, including hypoglycemia, hypocalcemia, and hyperbilirubinemia.

All women with gestational diabetes should receive appropriate nutritional and exercise counseling. If dietary management does not consistently maintain the fasting blood glucose concentration below 105 mg per deciliter or the 2 hour postprandial glucose concentration below 120 mg per deciliter, insulin therapy should be initiated. Oral hypoglycemic agents are contraindicated during pregnancy. If insulin is prescribed, human preparations are preferred to minimize antigenicity.

Women who had gestational diabetes should be evaluated at the first postpartum visit by a 2-hour, 75-g glucose tolerance test to detect overt diabetes.