Gestational diabetes: a threat to mom and baby
At my 26-week OB appointment, I drank a bottle of extra-sweet soda—imagine Mountain Dew spiked with pancake syrup—and an hour later, submitted my arm for a blood test. I was being screened for gestational diabetes and, as a gym regular and healthy eater (except for those first-trimester French-toast binges), I wasn't worried.
But the next day I learned that my blood sugar exceeded the cutoff level, and I'd need a more precise test involving an overnight fast, four blood draws and a soda twice as sweet as the first. This time I was worried. What were the chances that I could actually have gestational diabetes? If so, what would that mean for me and the twins I was carrying? How concerned should I be?
These are hot-button questions in the medical community. High blood sugar during pregnancy, what doctors call gestational diabetes mellitus (GDM), now affects 5 percent to 8 percent of expectant women, up from 4 percent about 20 years ago. Doctors have known for decades that GDM puts women at risk for having large babies and Cesarean sections; new studies indicate it may have long-term consequences and that it poses risks at lower blood-sugar levels than previously thought. The good news is that proper treatment reduces these risks. A diagnosis might sound scary, says Danielle Symons Downs, Ph.D., an assistant professor of kinesiology at Pennsylvania State University in University Park, "but for a woman who takes it seriously and makes lifestyle changes, it could be the best thing to happen to her and her offspring."
The sugar story
Gestational diabetes develops when hormones from the placenta compromise a woman's ability to use the insulin produced by her pancreas. Though most women compensate by producing extra insulin to break down glucose (blood sugar) for energy, some can't; their excess glucose builds up in the blood and passes through the placenta. "In some pregnancies with GDM, the baby sucks up the mother's glucose and grows bigger than it should," Downs explains. "In others, the baby is underdeveloped and has a low birth weight."
After delivery, mom's blood sugar levels typically revert to normal, but according to a study of nearly 10,000 mother-child pairs, this may not be the end of the story. Researchers at Kaiser Permanente Center for Health Research in Portland, Ore., and Hawaii, found that the higher a mother's blood sugar during pregnancy, the more likely her baby would be overweight by age 7. "Quite a few studies have shown that if you're overweight at ages 5 to 7 you're much more likely to be overweight as an adult," says endocrinologist Teresa Hillier, M.D., the study's lead author. Hillier found an increased risk of childhood obesity even among GDM babies who weren't born large. "To me, that suggests something has been metabolically changed that allows the baby to more easily store fat," she says.
Hillier found the risks were reduced when mothers were treated with diet changes and increased exercise and, if that was insufficient, by adding medication, typically insulin. When women remained untreated, their baby's risk of being overweight or obese at ages 5 to 7 was nearly twice as high, "but the children of women who were treated for GDM had no greater risk of overweight or obesity compared with children of mothers with normal blood sugar during pregnancy," she says. "This suggests that treating moms during pregnancy gives their babies a fighting chance for a normal metabolism."
But who should receive treatment? Despite the new research, there's no consensus on the threshold for gestational diabetes or even whether mild cases warrant intervention. "We don't know the level of glycemia [high blood sugar] that truly poses a risk to the fetus," says Mark Landon, M.D., vice chairman of the department of OB/GYN at Ohio State University Medical Center in Columbus, who is studying the effectiveness of treating mild GDM.
The world's top gestational diabetes researchers will convene later this year to analyze the research and possibly lower the blood-sugar levels that indicate a diagnosis. "There's a good chance [lowering the threshold] will result in more women being identified," says Boyd Metzger, M.D., a professor of medicine and endocrinology at Northwestern University and lead investigator of a GDM study involving 23,000 pregnant women in nine countries. "We found that some problems occurred even in ranges previously considered normal for pregnant women," he adds. Among Metzger's results: moms-to-be with the highest blood-sugar levels were four to six times more likely to deliver large babies than women with the lowest levels.