ADA 2010: Updated diagnosis, drug guidelines in gestational diabetes

New data are changing the way gestational diabetes is diagnosed and treated. Veteran diabetes educator Donna Jornsay, RN, BSN, PNP-C, CDE, North Shore-Long Island Jewish Health System, Lake Success, New York, laid out the current guidelines during a Tuesday morning seminar, The Art and Science of Gestational Diabetes Counseling.

“Our initial diagnostic criteria for gestational diabetes were used to define who was at risk,” Jornsay explained. “They were not designed to assess perinatal outcomes. That is why the diagnostic criteria have been updated.”

The current criteria are based on the HAPO (Hyperglycemia and Adverse Pregnancy Outcomes) trial that was first presented at the ADA Scientific Sessions in 2007. The cutoff for gestational diabetes has been set at either a fasting plasma glucose level of 92, a 1-hour oral glucose tolerance test plasma glucose level of 180, or a 2-hour plasma glucose level of 153. Fasting glucose alone identifies gestational diabetes in about 8.3% of pregnant women. Adding 1-hour plasma glucose identifies 14%, and adding a 2-hour plasma glucose identifies 16.1%.

If test results are below the cutoffs for gestational diabetes, the woman should be rechecked at 24 to 28 weeks with an oral glucose tolerance test.

“If any one of those tests is positive for overt diabetes, treat as existing diabetes, not gestational,” Jornsay advised. “It is not going to go away at the end of pregnancy.”

At the same time, altering risk factors by lowering blood pressure and low-density lipoproteins have protective effects on both coronary artery disease and glucose control.

The current strategy is to screen all women at the initial prenatal visit, she continued. Studies show that 40% of women with gestational diabetes have no overt risk factors.

“Another change is that you need only 1 abnormal value to make the diagnosis during pregnancy,” said Jornsay.” You have to have all 3 values be normal to have normal glucose tolerance.”

Treatment recommendations are also changing. Although no oral antidiabetic agents have FDA approval for use during pregnancy, some agents have come into common use.

Sulfonylureas are not recommended because of high rates of fetal malformation.

Metformin should also be avoided during pregnancy. There are conflicting data showing both significant associations with preeclampsia and stillbirths and no significant associations with fetal malformations.

Glyburide appears to be safe during pregnancy. Data published in 2000 found minimal transport across the placental barrier, no evidence of drug in cord blood, and no change in neonatal abnormalities. “Many people have been using glyburide for gestational diabetes over the past decade,” Jornsay reported.”

Other oral agents, including thiazolidinediones, meglitinides, and alpha-glucosidase inhibitors, have not been studied during pregnancy.