Using HAPO data, the IADPSG proposed a new set of GDM diagnostic criteria in 2010, which has been adopted by ADA and AACE in 2011.3-6 Following the new standards, all women not previously diagnosed with diabetes should be screened at 24 to 28 weeks’ gestation using a 75-g, 2-h oral glucose tolerance test (OGTT) after an 8-h overnight fast. The diagnosis of GDM is made if there is one abnormal plasma glucose value: fasting glucose ≥ 92 mg/dL, 1-h glucose ≥ 180 mg/dL, or 2-h glucose ≥ 153 mg/dL.
Q: What are the goals for self-monitoring of blood glucose (SMBG) in pregnancy?
HAPO revealed that fasting and postprandial hyperglycemia all predicted risk for macrosomia, fetal hyperinsulinemia, and cesarean delivery.3 ADA and AACE concur with the recommendations from the Fifth International Workshop-Conference on Gestational Diabetes that SMBG goals for women with GDM are as follows: preprandial ≤ 95 mg/dL and either 1-h postprandial ≤ 140 mg/dL or 2-h postprandial ≤ 120 mg/dL.5,6,23
SMBG is recommended at least three times daily for pregnant women taking insulin, but ADA also recommends that monitoring be dictated by the needs and goals of the patient.5 For women with T1DM and T2DM who become pregnant, ADA and AACE concur with a recent consensus statement recommending avoidance of excessive hypoglycemia while aiming for glycemic goals of: preprandial, bedtime, and overnight glucose, 60 to 99 mg/dL, peak postprandial glucose, 100 to 129 mg/dL, and A1C 5,6,24
Q: What is the best therapy for women with GDM?
Although more women will be diagnosed with GDM using the 2011 guidelines, therapeutic lifestyle changes and medical nutrition therapy (diet) will be key elements in their management, as demonstrated in the Maternal-Fetal Medicine Units Network and the Australian Carbohydrate Intolerance Study in Pregnant Women trials.25,26 Women should not arbitrarily restrict calories, as ketosis can result from simply an overnight fast, and maternal ketones have been shown to impair the IQ of offspring.27,28
In many cases, diet alone, while preventing ketonuria, may control postprandial plasma glucose, but diet-control is less successful when fasting hyperglycemia develops. When SMBG does not meet the established goals, ADA, AACE, and the American College of Obstetricians and Gynecologists (ACOG) concur that insulin is the first-line therapy, either via multiple daily injections or continuous subcutaneous insulin infusion.5,6,12
Regular and neutral protamine hagedorn (NPH) insulin, both of which are classified as pregnancy category B, have been the mainstay therapy. Recently, rapid-acting insulin aspart has been approved for use in pregnancy, and lispro is considered a treatment option for patients with GDM by AACE and the 2008 Expert Review of Obstetrics and Gynecology on the Management of GDM.6,29 Likewise, 70/30 aspart mix and 75/25 lispro mix are now pregnancy category B. For basal insulin, detemir appears to be safe during pregnancy in early studies, while glargine, though used, has no conclusive reports on safety30,31; both remain pregnancy category C.
Recent studies have indicated that pregravid BMI should also be considered by clinicians who treat GDM. Results showed overweight women with GDM that is well controlled on diet alone had a 50% greater risk for delivering a macrosomic infant than did normal-weight patients with GDM, and this risk increased twofold for obese women. Of note, overweight and obese women with GDM that was well controlled on insulin had no increased risk for fetal macrosomia, compared to the reference group.32
The oral medications metformin (pregnancy category B) and glyburide, the most widely studied sulfonylurea (pregnancy category C), have been shown to be effective alternatives to insulin without adverse effects in some women.6 However, the studies have been limited.
Long-term effects on children exposed to these medications in utero are yet to be determined, and randomized, prospective studies using oral diabetic medications in pregnancy, with long-term follow-up of mothers and offspring, are needed. (Consequently, in our practice, we only use insulin therapy for GDM.)
Q: What is the follow-up for women diagnosed with GDM?
Due to the prevalence of T2DM in women with GDM, ADA, AACE, and ACOG concur with the recommendations from the Fifth International Workshop-Conference on Gestational Diabetes that a 75-g, 2-h OGTT be administered six to 12 weeks after delivery in women with GDM who do not have diabetes immediately postpartum.5,6,12,23 Thereafter, ADA recommends resuming routine screening every three years, with more frequent testing depending on initial results and risk status.5 Education regarding diet, weight loss, and exercise should be presented as lifestyle changes and adopted by the entire family, since the infant is also at risk for obesity and the metabolic syndrome.