It's easy to dismiss gestational diabetes as a mild complication. It comes and goes during pregnancy, with usually no symptoms to speak of. It can disappear within hours after birth. Typically, women find out about the condition well into their pregnancies—at 24 to 28 weeks, and then only if they are screened for the condition by a doctor. It affects fewer than 10 percent of pregnant women.
Its causes, too, are mysterious: The way a woman's body changes to accommodate another life prompts a flood of hormones that places greater demands on the body's production of insulin, but why some women have trouble and others don't is still unclear.
And yet epidemiologist Erica Gunderson, PhD, a researcher at the Kaiser Permanente Division of Research in Oakland, Calif., takes gestational diabetes very seriously indeed. Current research shows that gestational diabetes (sometimes referred to as gestational diabetes mellitus, or GDM) may be a critical risk factor for diabetes in mothers and children later in life.
For years, gestational diabetes has been known to predispose women to type 2 diabetes later in life. Yet studies had not determined whether these women already had diabetes before pregnancy. Because it's diagnosed only in pregnancy and disappears within hours or days of birth, researchers only had the "after" picture, so to speak: data gathered from women after they were diagnosed and already in the midst of their pregnancies. What was needed was a snapshot of the "before," to get a sense of where the condition came from and whether some people were predisposed to get it.
To pin down the truth, Gunderson used data from the Coronary Artery Risk Development in Young Adults (CARDIA) study, which tracked the health of more than 2,400 women over two decades. Her research, partly funded with a grant from the American Diabetes Association (ADA), gave her a way to look at women's health before, during, and after pregnancy.
What she discovered was striking. According to the CARDIA data, pregnancy alone had no impact on a woman's likelihood of developing type 2 diabetes later in life. But women whose pregnancies were complicated by gestational diabetes were 4 times as likely to develop diabetes after pregnancy, even after factors like blood glucose levels before pregnancy, obesity, weight gain, and family history were accounted for. "Pregnancy, above and beyond weight gain, is a risk factor for diabetes in women," says Gunderson. "Pregnancy could possibly exhaust the pancreas and beta cells," making them more likely to malfunction or fail later in life.
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Published in the journal Diabetes in 2007, Gunderson’s study went a long way toward identifying the risk of diabetes in mothers who had had gestational diabetes. But what about their children? Gunderson recently began work on another ADA-funded project that examines the relationship between gestational diabetes and the health of children. The research is part of a study dubbed SWIFT Offspring, or the Study of Women, Infant Feeding and Type 2 Diabetes in the Offspring.
"It's the mother-infant dyad that is the focus of the research now," she says. Babies of women with untreated GDM tend to be larger than average and may develop jaundice or hypoglycemia as newborns. Prior research shows that children of mothers with gestational diabetes may encounter complications later in life, too. "The offspring of women with gestational diabetes are at higher risk for obesity and developing the metabolic syndrome," the collection of weight and endocrine issues that place people at higher risk for type 2 diabetes down the road.
Erica Gunderson, PhD
Division of Research,
ADA Clinical Research Award
One theory is that conditions in the womb serve as a sort of blueprint for the body's development later in life. For the fetus, gestational diabetes may be an early introduction to diabetes, raising the risks after the baby is born. "During gestation, there may be some programming of metabolic parameters, and that may have long-term ramifications for future health," says Gunderson. With a grant from the ADA, Gunderson is now following mothers and kids for two years after birth.
She's starting her look at the long-term effects of gestational diabetes with an examination of whether breast-feeding can affect weight gain in the first year of life and reduce the risks of becoming overweight in childhood. (Formula-fed babies tend to grow much faster.) "Studies show the rate of growth in the first year of life may influence weight gain later in life," Gunderson says.
Better understanding how GDM affects mothers—and why—could lead to intervention programs designed to short-circuit the connection. One idea, Gunderson suggests, is to help women who show an increased risk of developing type 2 diabetes lose weight before they even become pregnant, giving them a cushion against the metabolic changes and weight gain brought on during pregnancy.