Obese women who undergo bariatric surgery have substantially lower rates of hypertensive complications during pregnancy, a large retrospective study found.

Compared with women who had bariatric surgery at a later time, those who had the surgery before delivery were 75% less likely to have any hypertensive disorder during pregnancy (OR 0.25, 95% CI 0.15 to 0.40), Wendy L. Bennett, MD, and colleagues from Johns Hopkins reported online in BMJ.

They also were less likely to have these specific hypertensive complications:

  *  Pre-eclampsia and eclampsia (OR 0.20, 95% CI 0.09 to 0.44)
  * Chronic hypertension complicating pregnancy (OR 0.39, 95% CI 0.20 to 0.74)
  * Gestational hypertension (OR 0.16, 95% CI 0.07 to 0.37)

Maternal obesity is a recognized risk factor for adverse perinatal outcomes, including gestational diabetes, hypertension, and congenital anomalies.

Maternal hypertension itself is associated with adverse outcomes such as preterm birth and intrauterine growth restriction.

In addition, the risk of cesarean delivery is almost three times greater for women with class II obesity (body mass index 35 or higher).

“Although the pathophysiology of these disorders is complex and not yet completely understood, interventions that reduce obesity have the potential to decrease their incidence and associated complications,” the investigators wrote.

While some evidence existed suggesting that bariatric surgery can help reduce these risks, large studies had not examined the impact of the surgery and the severity of hypertensive disorders in pregnancy.

To assess this, Bennett and colleagues undertook a retrospective analysis of claims data from seven insurance plans in various parts of the country.

Among a sample of 585 obese women who had insurance claims for both delivery and bariatric surgery, the birth occurred before the mother had surgery in 269, and the delivery took place after the surgery in 316. In more than 80% of cases, the procedure used was gastric bypass.

Women whose deliveries took place before surgery were younger (31.3 versus 32.5 years, P<0.002) but had higher rates of pre-existing diabetes (23.4% versus 12.3%, P<0.001) and gestational diabetes (25.7% versus 13%, P<0.001).

Women who delivered before having surgery had higher rates of pre-eclampsia or eclampsia (15% versus 3%, P<0.001).

Those who gave birth before having the surgery also had higher rates of other hypertensive disorders:

* Gestational hypertension, 13% versus 2.5%, P<0.001
* Chronic hypertension complicating pregnancy, 13.8% versus 5.4%, P<0.001
* Pre-eclampsia or eclampsia with pre-existing hypertension, 12% versus 1%, P<0.001

The results have important clinical, public health, and policy implications, according to the researchers.

"Women who are of reproductive age can use this study to have a dialogue with their providers about the possibility of having bariatric surgery before pregnancy to reduce their risk of hypertension," lead author Bennett told MedPage Today.

The data also support insurance policies that cover bariatric surgery to improve pregnancy outcomes.

Strengths of the study include its use of a large claims database and its design, which did not present the difficulties associated with finding matched controls.

Limitations included the lack of individual clinical information such as height, weight, and parity, the possibility of erroneously entered diagnostic codes, and the selection bias and confounding inherent in observational studies.

Additionally, according to Bennett, the study did not examine possible complications of bariatric surgery in pregnancy.

Commenting on the study, Paresh C. Shah, MD, of Lenox Hill Hospital in New York said, "It has been known for some time that effective weight loss achieved through bariatric surgery has a positive impact on fertility in women with morbid obesity, but this paper addresses another major concern of pregnancy and obesity - namely, risk to mother and baby."

The study demonstrates with "clear and convincing data taken from the payor community that there is a tremendous reduction in risk if women of childbearing age have successful bariatric surgery prior to pregnancy," said Shah.

The authors of the study concluded, "Future research should address long-term maternal and child health after pregnancies and deliveries after bariatric surgery in terms of weight management, nutritional status, and burden of long-term chronic disease."

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Primary source: BMJ
Source reference:
Bennett W, et al “Impact of bariatric surgery on hypertensive disorders in pregnancy: retrospective analysis of insurance claims data” BMJ 2010; doi:10.1136/bmj.c1662.