Gestational Diabetes Developing into Type 2 Diabetes Postpartum: A Growing Problem

Gestational diabetes mellitus can have lasting implications for the pregnant woman and her baby. Steven G. Gabbe, MD, Senior Vice President for Health Sciences and CEO, Ohio State University Medical Center, discussed gestational diabetes at the 2010 American College of Obstetricians and Gynecologists (ACOG) annual meeting.

“Alarmingly, type 2 diabetes is increasing rapidly in pregnancy—especially in young women,” he said. “We’re seeing more teenage women who are pregnant and have diabetes.”

Dr Gabbe stressed the importance of screening for gestational diabetes, stating that it is wrong to take a lax approach and think that the condition will go away when the woman delivers. Instead, gestational diabetes provides a “sneak peek for us into the future of the woman’s metabolic problems,” he said.

Risks for Mother and Baby
Between 35% and 60% of women with gestational diabetes will develop type 2 diabetes, especially within the first decade postpartum. In terms of risk, women with gestational diabetes face a 7-fold higher risk of developing type 2 diabetes compared with their non–gestational diabetes counterparts. These women also have a shorter life expectancy, he said.

“We have to screen for gestational diabetes mellitus,” Dr Gabbe said. “If we don’t, we can’t treat it.”

When gestational diabetes is untreated, the consequences for the newborn can be:
Macrosomia
Large fetus for gestational age
Trauma, including shoulder dystocia
Hypoglycemia
Hypocalcemia
Jaundice.

In addition, the neonate born to a mother with gestational diabetes can develop other problems—including type 2 diabetes—later in life, he said.

Screening
Women who are severely obese and have a history of gestational diabetes or a strong family history of diabetes are considered at high risk for gestational diabetes and should be tested at the first opportunity.

Those who have 1 or 2 risk factors are at average risk and should be tested between 24 and 28 weeks of gestation.

Low risk for gestational diabetes includes:

• Age <25 years
• Normal weight
• No first-degree relative with diabetes, personal history of diabetes, or poor obstetric outcome
• Not of an ethnicity that places them at higher risk for diabetes (ie, African American, American Indian, Asian American, Hispanic, or Pacific Islander).

Health practitioners should screen patients using a 50-g glucose load, or in high-risk women, a diagnostic oral glucose tolerance test, he said.

Changing Guidelines
The diagnostic criteria for gestational diabetes have changed over the years, establishing lower cutoff levels. The glucose level thresholds for a diagnosis of gestational diabetes recommended by the American Diabetes Association and ACOG are:

• Fasting plasma glucose ≥95 mg/dL
• 1-hour plasma glucose ≥180 mg/dL
• 2-hour plasma glucose ≥155 mg/dL
• 3-hour plasma glucose ≥140 mg/dL.

An even higher prevalence of gestational diabetes could emerge if results of the Hyperglycemia and Adverse Pregnancy Outcome (HAPO) study are used to create new standards, Dr Gabbe said. The HAPO study demonstrated a strong relationship between maternal glucose levels that fell below the current threshold for gestational diabetes and birth weight and body fat percentage >90th percentile, cesarean delivery, neonatal hypoglycemia, and cord C-peptide >90th percentile.

Dr Gabbe said he was unsure when these new standards may be adopted.

“I just think it is going to be some time before folks agree, because it does increase the number of women with gestational diabetes dramatically,” he said.

Gestational diabetes currently affects 7% of all pregnancies in the United States, and that number would more than double if the HAPO standards are adopted, he said. Recommendations resulting from the HAPO study’s findings would entail:

• Fasting plasma glucose ≥92 mg/dL
• 1-hour plasma glucose ≥180 mg/dL
• 2-hour plasma glucose ≥153 mg/dL.

Treatment during Pregnancy
The good news is that “treatment does work,” Dr Gabbe said. Lifestyle recommendations include a diet consisting of 3 balanced meals and a bedtime snack, plus 30 minutes of daily exercise.

If lifestyle modifications alone do not keep gestational diabetes under control, oral agents can be used. Glyburide is an option, but it has been shown to get through the placenta, with 70% of the level in the mother being detected in the fetus, Dr Gabbe said. He therefore recommended not exceeding 20 mg/day of glyburide for the treatment of gestational diabetes.

Studies have shown that women with gestational diabetes receiving treatment with metformin, the common diabetes medication, had an increased rate of preterm birth, and 46.3% needed supplemental insulin. Other studies, however, have shown no evidence of adverse maternal or neonatal outcomes with this drug, Dr Gabbe pointed out. Overall, diet and exercise are the best and safest treatments, but glyburide, insulin, or metformin can all be safely used, he said. It is also crucial to check fasting and 1- and 2-hour postprandial glucose levels daily.

Postpartum Follow-up
Monitoring plasma glucose levels remains important after the woman gives birth, Dr Gabbe said. Fasting plasma glucose levels should be checked after delivery, at 1 year postpartum, and then every 3 years, although some recommend annual checks, he added. “We have to continue to follow the patient,” Dr Gabbe said.