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What are the difficulties in treating gestational diabetes?
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No data on long-term benefits of therapies for mother and baby.
There are many hurdles in treating gestational diabetes — usually identified in mid-pregnancy — and there is limited time to improve glycemic control. Also, there are limited therapies available, especially therapies that match the basic underlying pathophysiology of increased insulin resistance. Currently, there are no data to determine which therapies are best for long-term outcomes for the mother and baby, although recent studies have shown short-term benefits with metformin and insulin.
Metformin is easier to use and addresses the increased insulin resistance that occurs during pregnancy. My concern is that we do not have long-term data on the outcomes in childhood and adulthood for infants exposed to metformin in utero. It is possible that their outcomes would be superior to those exposed to hyperglycemia without treatment or to insulin but we do not have any data on this.
Insulin analogs, especially long-acting analogs such as glargine and detemir, may be easier to use during pregnancy but there are no data to support their safety during pregnancy. Insulin can provide the most rapid improvement in glucose control but requires close monitoring of blood glucose and education on how to inject insulin, and increases the risk for both hypoglycemia and weight gain. Metformin plus diet and exercise addresses insulin resistance, minimizes the risk for hypoglycemia and weight gain, but can take longer to have an effect.
Use of metformin during pregnancy has several advantages over insulin. First, it is easier to use for most women who are not currently taking insulin. Second, it could help prevent excess weight gain that predisposes women to antenatal risks for both the mother and baby. Third, it might provide a long-term benefit for children through positive effects on weight and risk for long-term metabolic effects.
Linda Lester, MD, MS, is Assistant Professor of Medicine in the Division of Endocrinology, Diabetes and Clinical Nutrition at Oregon Health & Science University.
Choosing the best therapy to control blood glucose.
It is possible to identify gestational diabetes earlier in pregnancy by screening patients with high-risk factors, such as history of disease, elevated BMI and women aged 35 years and older. Otherwise, screening is recommended between 24 weeks and 28 weeks gestation. Once gestational diabetes is diagnosed, proper treatment is important in preventing complications such as macrosomia, shoulder dystocia and birth trauma. Most women can control their blood glucose with dietary modification and moderate exercise. Considering gestational diabetes carries up to 50% risk for developing diabetes later in life, this provides an excellent opportunity to educate women on the importance of maintaining a lifelong commitment to a healthy diet and exercise.
However, about 15% of women require medication to control their blood glucose. Insulin has been the gold standard for treating gestational diabetes because it is safe and effective. While insulin can cause hypoglycemia, that risk is greatly outweighed by the potential benefits.
The most well studied oral medication is glyburide, as opposed to metformin. In a head-to-head comparison with insulin, glyburide was found equally as effective and safe as insulin. Like insulin, glyburide can produce hypoglycemia. Conversely, studies comparing metformin to insulin found that half of the patients receiving metformin required additional insulin to achieve optimal glucose levels.
In fact, the ADA and American College of Obstetricians and Gynecologists currently recommend using only insulin for gestational diabetes. If an oral medication is prescribed, there are better data supporting the use of glyburide rather than metformin at this time.
Gema Fernandez, MD, is an OB/GYN at Banner Estrella Medical Center in Phoenix.