Women who have had bariatric surgery are far less likely to experience serious hypertensive disorders during pregnancy, including pre-eclampsia and eclampsia, than women who have yet to undergo the surgery, according to new research.
Investigators found a 75% reduction in the odds of being diagnosed with a hypertensive disorder in pregnancy in those who had undergone the surgery, compared with their counterparts.
For their study, Dr. Wendy L. Bennett and colleagues at the Johns Hopkins University School of Medicine, Baltimore, evaluated claims data from 7 private insurance plans to find 585 U.S. women between the ages of 16 and 45 who had undergone bariatric surgery for weight loss and had at least one prior pregnancy and delivery (BMJ 2010 Apr. 13;340:c1662 [doi: 10.1136/bmj.c1662]).
A total of 269 of the women delivered their babies before gastric bypass surgery or another weight-loss surgery, and 316 delivered afterward. For the first group, the mean time from delivery to surgery was 17.9 months, and for the second, the mean time from surgery to delivery was 23.6 months. Gastric bypass surgery accounted for 81.5% of procedures overall, with other surgeries, such as adjustable gastric banding, making up the rest. The mean age of the women was 31.9 years at delivery and 31.5 years at surgery.
In the group that delivered before having surgery, 31.2% of the women were diagnosed with a hypertensive disorder—from chronic and gestational hypertension to pre-eclampsia and eclampsia alone or superimposed on hypertension—between the start of pregnancy and two weeks after birth, while only 9.8% of the post-surgery group did, even after adjusting for factors such as age at delivery, multiple pregnancy, the type of surgery, and pre-existing diabetes.
Pre-eclampsia or eclampsia was diagnosed in 14.5% of women in the presurgery group and 2.5% in the postsurgery group. “We went 2 weeks postpartum, because we wanted to make sure we got all the diagnoses,” Dr. Bennett said in an interview. “Women can get postpartum pre-eclampsia.”
The Hopkins findings confirm those from an earlier Israeli study of similar design (Int. J. Gynecol. Obstet. 2008;103:246-51), which found the rate of a composite of hypertensive disorders during pregnancy to be more than halved after bariatric surgery.
The Hopkins team saw an even more dramatic reduction—about 75%—in the odds of all hypertensive disorders in pregnancy, and was able to isolate all severities of hypertensive disorders by analyzing outpatient and inpatient codes for each. Further, Dr. Bennett and colleagues wrote that they were “able to describe outcomes of chronic hypertension complicating a pregnancy and pre-eclampsia superimposed on chronic hypertension among women who have had bariatric surgery.” Chronic hypertension in pregnancy and pre-eclampsia, the authors noted, can increase the long-term risk of chronic disease in the mother, including cardiovascular and renal disease.
Dr. Bennett noted that her team reviewed relatively new and geographically diverse data (the claims were dated from 2002 to 2006, from more than one region of the United States), compared with other recent studies on bariatric surgery and pregnancy. This afforded the authors an up-to-date picture reflecting outcomes from surgeries currently performed, she said.
The team's dataset lacked height and weight information for subjects before and after surgeries, though all had been diagnosed as obese (body mass index of 35 kg/m
The authors noted a further limitation to their study, which was the possibility of selection bias and confounding by indication. For example, they wrote, “an obese woman with gestational hypertension might have been more likely to subsequently undergo bariatric surgery if she developed chronic hypertension after her pregnancy or had other comorbidities associated with obesity making her eligible for bariatric surgery. If this occurred, the number of diagnoses of hypertensive disorder in pregnancy in the women who delivered before surgery could be increased and bias our results.”
None of the authors declared any conflicts of interest.