In July 2017, a new American Congress of Obstetricians and Gynecologists study was released on Gestational Diabetes Mellitus (GDM). This study contains important new information on both the management and treatment for GDM.
Gestational diabetes that is adequately controlled without medication is often considered diet-controlled GDM or class A1GDM. Gestational diabetes mellitus that requires medication to achieve normal blood sugar levels is often called class A2GDM. It has been estimated that 6–9% of pregnancies are complicated by diabetes. Caucasian women generally have the lowest rates of GDM. There is an increased prevalence of GDM among Hispanic, African American, Native American, and Asian or Pacific Islander women. Gestational diabetes also increases with the same risk factors seen for type 2 diabetes such as obesity and increased age. With a greater prevalence of obesity and sedentary lifestyles, the prevalence of GDM among reproductive-aged women is increasing globally.
Women with GDM have a higher risk of developing preeclampsia (9.8% in those with a fasting glucose less than 115 mg/dL and 18% in those with a fasting glucose greater than or equal to 115 mg/dL) and undergoing a cesarean delivery (25% of women with GDM who require medication and 17% of women with diet-controlled GDM underwent cesarean delivery versus 9.5% of controls). Furthermore, women with GDM have an increased risk of developing diabetes (predominantly type 2 diabetes) later in life. It estimated that up to 70% of women with GDM will develop diabetes within 22–28 years after pregnancy. In 2014, the U.S. Preventive Services Task Force made a recommendation to screen all pregnant women for GDM at or beyond 24 weeks of gestation.
How are Patients Tested for GDM?
The two-step approach to testing for GDM that is commonly used in the United States is based on first screening with the administration of a 50-g oral glucose solution, followed by a 1-hour venous glucose determination. The American College of Obstetricians and Gynecologists (ACOG) supports the two-step process Women whose glucose levels meet or exceed an institution’s screening threshold then undergo a 100-g, 3-hour diagnostic OGTT. Historically, gestational diabetes mellitus is most often diagnosed in women who have two or more abnormal values on the 3-hour OGTT
The new ACOG guideline provides information about the changes in the diagnosis of GDM – Women who have even one abnormal value on the 100-g 3-hour OGTT have a significantly increased risk of adverse perinatal outcomes compared with women with GDM. Therefore, one elevated value, as opposed to two, may be used for the diagnosis of GDM.
What are the benefits of treating gestational diabetes mellitus?
The 2005 Australian Carbohydrate Intolerance Study in Pregnant Women trial, the first large-scale (1,000 women), randomized treatment trial for GDM (36) found the treatment was associated with a significant reduction in the rate of the primary outcome, a composite of serious newborn complications (perinatal death, shoulder dystocia, and birth trauma, including fracture or nerve palsy). Treatment also reduced preeclampsia (from 18% to 12%) as well as reduced the frequency of infants who were large for gestational age (LGA) (from 22% to 13%) and who had a birth weight greater than 4,000 g (from 21% to 10%).
Additionally, the rates of cesarean delivery, shoulder dystocia, and hypertensive disorders were significantly reduced in women who were treated for GDM. A U.S. Preventive Services Task Force systematic review underscored the demonstrated benefits of treating GDM and highlighted the reduced risks of preeclampsia, shoulder dystocia, and macrosomia. The treatment in such studies has consisted of dietary counseling with specific nutritional approaches and exercise.
Based on this evidence, women in whom GDM is diagnosed should receive nutrition and exercise counseling, (i.e meet with a dietician if possible) The ADA recommends nutritional counseling by a registered dietitian and development of a personalized nutrition plan based on the individual’s body mass index for all patients with GDM. When this fails to adequately control glucose levels, medication should be used for maternal and fetal benefit. It is important to note that in both trials described above, women with elevated glucose values were treated with insulin, not oral agents when medical nutrition treatment did not control glucose values.
How Can Patients Lessen their Chances of Contracting GDM?
A diet composed of 50–60% carbohydrates often will result in excessive weight gain and postprandial hyperglycemia. Therefore, it has been suggested that carbohydrate intake be limited to 33–40% of calories, with the remaining calories divided between protein (20%) and fat (40%)
A small, recent randomized trial demonstrated that women with GDM randomized to a complex carbohydrate diet had lower fasting glucose values as compared with those on a conventional diet. Given these findings and the results of other treatment trials, complex carbohydrates are recommended over simple carbohydrates because they are digested more slowly, are less likely to produce significant postprandial hyperglycemia, and potentially reduce insulin resistance. There is little evidence evaluating or supporting different dietary approaches to the treatment of GDM. In practice, three meals and two to three snacks are recommended to distribute carbohydrate intake and to reduce postprandial glucose fluctuations.
What pharmacologic treatments are effective in managing gestational diabetes mellitus?
Pharmacologic treatment is recommended when target glucose levels cannot be consistently achieved through diet changes and exercise. Insulin historically has been considered the standard therapy for GDM management in cases refractory to nutrition therapy and exercise and this has continued to be reinforced by the ADA. Oral antidiabetic medications (e.g., metformin and glyburide) increasingly are being used among women with GDM, even though they have not been approved by the U.S. Food and Drug Administration for this indication and even though insulin continues to be the ADA-recommended first-line therapy
The NEW ACOG 2017 guideline has changed to align with ADA recommendations and suggests insulin as the first line of medical therapy for GDM.
ACOG PRACTICE BULLETIN Gestational Diabetes Mellitus Number 180, July 2017
Carnegie Imaging for Women blogs are intended for educational purposes only and do not replace certified professional care. Medical conditions vary and change frequently. Please ask your doctor any questions you may have regarding your condition to receive a proper diagnosis or risk analysis. Thank you!