For reasons unclear, the babies of obese women are less likely to be born preterm than those of women of normal weight, even though the various stresses caused by obesity might be expected to increase the likelihood of premature birth. A new study by Judette Louis, M.D., M.P.H., a member of the 2008 cohort of Robert Wood Johnson Foundation Physician Faculty Scholars, adds a new and important piece to this medical puzzle: Women who suffer from obstructive sleep apnea—the great majority of whom are obese—are actually more likely to deliver prematurely, and to face a variety of other complications during their pregnancies. In short, the apparent relationship between obesity and the likelihood of carrying babies to term seems to be reversed for women with obstructive sleep apnea.
Louis is assistant professor of obstetrics and gynecology at Case Western Reserve University School of Medicine. She and colleagues from Case Western and Wayne State University School of Medicine studied the experiences of 57 women who had delivered babies at the Case Western-affiliated MetroHealth Medical Center between 2000 and 2008. All the women had previously been diagnosed with obstructive sleep apnea (OSA)—sleep apnea caused by a physical obstruction of the airway, as opposed to an imbalance of the brain’s respiratory control centers. About 85 percent of the women in the group were obese, according to the researchers, reflecting the common association between obesity and obstructive sleep apnea.
The research team compared these women’s experiences with those of more than 200 women who had delivered babies during the same time period. Half of these women were obese and half not, and none had been diagnosed with sleep apnea.
Some of what they found was expected, but some was a surprise. The research revealed that the women with OSA had more complications during their pregnancies, including preeclampsia, cesarean sections and preterm delivery. The preterm finding ran counter to expectations because so many of the women with OSA were obese, and would thus have been expected to have fewer premature births. However, in this group most of the preterm deliveries were because of the development of maternal life-threatening conditions such as severe preeclampsia or cardiovascular disease. Another finding that surprised the research team was that the babies of the women with OSA were more likely to spend time in the neonatal intensive care unit.
“My hypothesis is that OSA is a marker of the end-stage effects of obesity,” Louis says. “These women are more likely to have other obesity related medical conditions too, including hypertension and diabetes. There are some people who are obese but whose bodies haven’t yet experienced all the ramifications of the obesity. Given time, they will likely develop those conditions.”
As part of her participation in the Physician Faculty Scholars program, Louis is working to develop a cost-effective screening tool—a questionnaire—for OSA in pregnant women. “When I was a resident,” she recalls, “I noticed that we’d often have obese women come in to deliver babies, who would become hypoxic. The only cause we knew for that was a pulmonary embolism, so the women would have extensive testing—only to eventually discover that they actually had sleep apnea…. We hope that providers will be able to use the tool we’re developing to identify at-risk women, so they can help women have better outcomes for their pregnancies. If we can diagnose sleep apnea, we can treat it, primarily with weight loss. But even women who are pregnant and who shouldn’t be dieting would benefit from screening, because if we can identify that they’re at risk for preeclampsia and preterm delivery, the women can be counseled to deliver at hospitals that can deal with high-risk situations.”
Louis’ study, “Maternal and neonatal morbidities associated with obstructive sleep apnea complicating pregnancy,” was published in the March 2010 issue of the American Journal of Obstetrics and Gynecology.