Early Screening May Prevent Type 2 in Women With Gestational Diabetes
Erika Werner, MD, MS
Maternal and Infant Care Specialist, Women & Infants Hospital of Rhode Island
American Diabetes Association Research Funding
Clinical Research Grant
Diabetes diagnosed during the second or third trimester of pregnancy is known as gestational diabetes, and it affects 7 percent of pregnant women in the United States.
While researchers don’t know exactly what causes it, they do know that pregnancy hormones can make women more resistant to insulin—that is, they need more insulin to manage blood glucose levels.
Usually, blood glucose goes back to normal shortly after delivery. But gestational diabetes can be a warning sign. More than half of women who have gestational diabetes while pregnant will develop type 2 diabetes eventually. “Gestational diabetes is a screening test for diabetes in and of itself,” says Erika Werner, MD, MS, director of the Division of Maternal-Fetal Medicine at Women & Infants Hospital in Providence, Rhode Island. “If you get diabetes in pregnancy, it goes away after delivery, but it reveals you may be at high risk for diabetes as you get older.”
Women with a history of gestational diabetes are often asked to return for a diabetes screening about a month after giving birth. The standard test is an oral glucose tolerance test: A doctor will check a woman’s blood glucose before and two hours after she drinks a sugary drink. (It’s the same test used to identify gestational diabetes during pregnancy and to diagnose other forms of diabetes.)
Elevated blood glucose levels—between 140 and 199 mg/dl—two hours after downing the sweet drink indicate prediabetes (or impaired glucose tolerance). The condition is a risk factor for type 2 diabetes. “The ones with normal sugar and no signs of prediabetes are at much lower risk,” Werner says. “If you have impaired glucose tolerance, those women have a 70 to 90 percent chance of getting diabetes.”
The problem, according to Werner, is that the standard oral glucose tolerance test takes at least two hours. For many brand-new mothers, that’s a big ask. As a young doctor, Werner heard a common refrain when she asked new moms to schedule an appointment to come back for a glucose tolerance test. “They’d say, ‘That’s really going to be challenging. Can’t you just do the test now?’ It’s hard to be someplace for two hours four to six weeks after giving birth,” she says. Her theory: Barriers such as lack of transportation, insurance, and child care may play a role in why women don’t return for their glucose test.
That got Werner wondering whether there was some reason for waiting a month to test. If it were possible to test women while they were still in the hospital, Werner reasoned, it might be easier for new moms to manage, increasing the number of women with gestational diabetes who were tested. “The more we can do during the postpartum hospitalization, the better,” Werner says. “When else is a young, healthy person in the hospital for one to four days?”
But first, Werner needed to show a glucose tolerance test given a day after giving birth is as powerful in terms of predicting diabetes risk as a test administered a month later. In 2016, Werner published a pilot study in the American Journal of Perinatology that showed just that. Now, with the help of a grant from the American Diabetes Association, she’s running a larger study, hoping to provide still more proof. She plans to give oral glucose tolerance tests to 300 women with gestational diabetes just after they give birth and then four to six weeks later.
A year after they deliver, she’ll test them all again. The idea is to compare the results of the tests taken in the hospital after delivery with results of tests taken after four to six weeks, then see if they’re both equally accurate in predicting glucose tolerance at the one-year mark. “We’re trying to prove the results are just as good postpartum day two as at four to six weeks,” Werner says.
That, in turn, could make it possible to screen more women—and improve their health. Women whose gestational diabetes is a warning sign for type 2 are great candidates for diabetes education and other treatments. “If we intervene with women who have gestational diabetes, we can reduce the risk of developing type 2 by 50 percent,” Werner says. “Right now, that’s not happening. We have a real opportunity to intervene postpartum.”
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