Obese women who have bariatric surgery before getting pregnant are at significantly lower risk for developing dangerous hypertensive disorders during pregnancy than those who don’t, according to a study of medical insurance records by Johns Hopkins experts.

Hypertensive disorders in pregnancy — which include gestational hypertension, preeclampsia and eclampsia — complicate an estimated 7 percent of pregnancies in the United States. Researchers say they are much more common in obese women, who make up a third of women of childbearing age.

“We have long known that women who have these blood pressure disorders are not only at an increased risk for pregnancy complications in themselves and their babies, but also for chronic diseases in the future,” says Wendy L. Bennett, M.D., M.P.H., assistant professor of medicine at the Johns Hopkins University School of Medicine and a study leader. “Can we prevent the development of these disorders in pregnancy with bariatric surgery? These findings suggest the answer may be ‘yes.’”

Results of the research are published online in the British Medical Journal.

For the study, Bennett and her colleagues looked at five years of data from Blue Cross Blue Shield insurance records and identified 585 women who had bariatric surgery and delivered a baby. The sample included 269 women who had babies some time before having weight-loss surgery and 316 who had the surgery before getting pregnant. More than 80 percent of the women chose gastric bypass surgery over other, less common weight-loss operations.

The researchers found an 80 percent reduction in the risk of preeclampsia and eclampsia among women who had surgery before pregnancy, along with a 74 percent reduction in the risk of gestational hypertension and a 61 percent reduction in the risk of chronic hypertension in pregnancy, all of which are known to cause pregnancy complications.

Bennett cautions that not every obese woman is a candidate for bariatric surgery. And not every obese woman wants to undergo the operation, which itself carries risks of complications. Moreover, insurance companies don’t always cover the surgery, and when they do, it’s typically not unless a woman has a body-mass index (BMI) of more than 40 or a BMI of more than 35 with a co-morbidity such as diabetes or sleep apnea, she says.

One limitation of the study is that the insurance data did not include information on fetal outcomes, so researchers can’t say what, if any, effect bariatric surgery may have on babies born to women who have undergone the operation, Bennett says. Babies born to mothers with preeclampsia or eclampsia may arrive prematurely which can lead to complications up to and including fetal death.

Nevertheless, Bennett says her study suggests that insurance companies “should be covering gastric bypass surgery in women of childbearing age because of the potential to reduce complications if we can reduce their weight before they become pregnant.” Treating the obesity before pregnancy, she adds, also has the potential of saving a lot of money on treatment of complications in mothers, fetuses and newborns.”

Bennett says her findings are intended to open a discussion between doctors and obese patients who wish to become pregnant about the risks and benefits associated with bariatric surgery. Once they become pregnant, women who have undergone weight-loss surgery will need to be closely monitored to make sure they and their fetuses are getting enough nutrition.

Prior research has shown that rates of gestational diabetes (which also causes complications in pregnancy) decreases after bariatric surgery, and that weight loss can increase fertility in obese women.

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Other Johns Hopkins authors on the study are Marta M. Gilson, Ph.D; Roxanne Jamshidi, M.D., M.P.H.; Anne E. Burke, M.D., M.P.H.; Jodi B. Segal, M.D., M.P.H.; Kimberly E. Steele, M.D.; Martin A. Makary, M.D., Ph.D.; and Jeanne M. Clark, M.D., M.P.H.

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