In a 33-year retrospective study, researchers from the University of Washington School of Public Health and UW Medical Center compared birth outcomes for infants born to mothers with a history of bariatric surgery to outcomes for infants born to mothers without weight-loss surgery.

In the United States, about one-fifth of women are obese at the time of conception. Previous studies have found that bariatric surgery, or procedures that cause weight loss by restricting the amount of food the stomach can hold, reduces pregnancy problems in obese women.

However, the new study, published in JAMA Surgery, showed that infants born to mothers with prior bariatric surgery had significantly higher risks for prematurity, neonatal intensive care unit admission, and being small for gestational-age status. The risk for perinatal complications were highest in those born to mothers with less than a two-year interval between operation and birth.

"We knew that women with a history of bariatric surgery are a high-risk group for childbirth,” said corresponding author Brodie Parent, who conducted research as an MPH student in the UW School of Public Health’s Department of Epidemiology. “Ours is some of the first data to look at their risk over time after recovery from the operation." Parent is now a general surgery resident at the UW School of Medicine.

"This study underscores the higher-risk status of this population and may indicate that a recently postoperative mother with underlying nutritional, metabolic and physiological changes is at an elevated risk for perinatal complications," the authors wrote.

Parent and collaborators emphasized that the study does not conclude that obese women of childbearing age should decline weight-loss surgery in order to have children.

“Undoubtedly, bariatric operations result in many health benefits for morbidly obese women of childbearing age and reduce obesity-related obstetrical complications,” the authors wrote. “Findings from this study should not deter bariatric surgeons from offering such therapy to this population.”

Although evidence pointed to increased complications among postoperative mothers, the risks are highest in the first three years and appear to diminish over time. With adequate time to adjust and heal, mothers appear to reap the benefits of weight-loss surgery without increasing fetal risk.

These findings could help health care professionals and postoperative patients determine optimal timing between surgery and conception.

Parent collaborated with Ira Martopullo, who earned an MPH from the School’s Department of Epidemiology, as well as Noel Weiss and Ali Rowhani-Rahbar, faculty members in the Department.