Gestational Diabetes Mellitus: What You Need to Know

Generally, diabetes mellitus (DM) is divided into 3 categories: type 1, type 2, and gestational. Gestational diabetes is becoming a greater concern as more of the population becomes overweight, and it can have serious consequences if left undiagnosed or uncontrolled.

Approximately 135,000 cases of gestational diabetes mellitus (GDM) are diagnosed each year in the United States. Risk factors include a family history of diabetes, increased body mass index (BMI), previous GDM, and advanced maternal age. Complications can occur in both the mother and the baby in GDM. Maternal complications include increased risk of cesarean section and chronic hypertension. It also is important to note that ~50% of women diagnosed with GDM will go on to develop type 2 diabetes. Risks for the baby include macrosomia (abnormally large size), hyperinsulinemia, congenital malformations, and stillbirth.

Screening criteria for GDM historically have been controversial. Although universal screening has been suggested by some, selective screening is practiced typically by most clinicians today. Women who do not require screening for GDM must meet all of the following criteria: age <25 years; normal body weight (BMI <25); not a member of any ethnic group with increased risk; and no family history of DM. Screening takes place between 24 and 28 weeks of gestation. It consists of a 50-g, 1-hour oral glucose tolerance test (OGTT). If the result is positive, then a second OGTT is performed with either a 75-or 100-g glucose solution, and diagnosis is confirmed if 2 or more results are abnormal (Table).

Glycemic control is of utmost importance during pregnancy to improve health outcomes for both the mother and the baby. The goals for blood glucose (BG) levels are stricter during pregnancy than traditional goals. Guidelines from the American Diabetes Association (ADA) recommend a fasting BG concentration of 60 to 90 mg/dL, a premeal BG of 60 to 105 mg/dL, and a 2-hour postprandial BG of <120 mg/dL. Self-monitoring of blood glucose (SMBG) must be individualized for each patient, but testing at least twice daily is suggested.

Medical nutrition therapy (MNT) and exercise are successful in controlling BG in 70% to 80% of women with GDM. The remaining 20% to 30%, however, will require insulin therapy to control diabetes during pregnancy. The ADA recommends the initiation of insulin therapy when MNT fails to keep fasting plasma glucose concentrations at =105 mg/dL or 2-hour postprandial glucose at =130 mg/dL. All human insulins, as well as the synthetic insulins lispro and aspart, are considered safe and effective for the mother and the baby during pregnancy.

Insulin currently is the only FDA-approved treatment for GDM management. Several small-scale studies, however, support the use of 2 oral agents during pregnancy?metformin and glyburide?and some clinicians are using them on a limited basis. Metformin, in particular, is commonly used in women with polycystic ovary syndrome during pregnancy and has shown no teratogenicity thus far. Some complications, such as higher rates of preeclampsia and stillbirths, have been seen with metformin, but the clinical significance is not yet known. Whether or not oral agents will be more commonplace in the future remains to be seen.

Counseling for patients with GDM must include a team approach to help patients meet proper glycemic control, weight control, nutritional, and exercise goals. A health care team may include the patient's physician, a nutritionist, and a pharmacist. Pharmacists can provide counseling to patients in many different areas: insulin education, injection technique and training, methods for prevention and treatment of hypoglycemia and hyperglycemia, and SMBG goals and technique.

Dr. Brian is a clinical specialist with Cornerstone Health Care, High Point, NC.