Bariatric Surgery May Increase Risk of Preterm Birth, Researchers Warn

Women who undergo weight loss surgery and then become pregnant appear to face a higher risk of experiencing a preterm delivery, according to the findings of new research. 

In a study published last week in the The New England Journal of Medicine, researchers at the Karolinska Institutet in Sweden indicate that women who lose weight after having bariatric surgery and then become pregnant have a higher risk of having a preemie when compared to women who did not have weight loss surgery.

The research focused on a group of women in Sweden who gave birth between 2006 and 2013. Researchers used data from the Scandinavian Obesity Surgery Registry and information on pregnancy characteristics was obtained from the Swedish Medical Birth Register.

A total of 1,941 women underwent bariatric surgery and then gave birth. This was compared to a control group of 6,574 women who did not have surgery but gave birth during that time. They were matched for maternal pre-surgery body mass index (BMI) or BMI during early pregnancy for the control group, age, smoking, and delivery year.

Overall, researchers found women who had bariatric surgery and then became pregnant had an eight percent risk of have a preterm delivery. This was compared to women who did not undergo the surgery, who had a six percent risk. Preterm was considered completing less than 37 weeks of pregnancy.

Findings of other studies have also linked bariatric surgery to other types of complications. A 2014 study concluded many patients who had gastric bypass surgery experienced complications such as requiring another surgery later and requiring re-hospitalization.

During this study, a total of 163 of the 1,941 women who underwent bariatric surgery delivered preterm compared to 447 of the 6,574 women who did not have bariatric surgery who delivered preterm.

The risk of moderately preterm birth, or delivery between 32 to 36 weeks of pregnancy, was also higher among women who had undergone bariatric surgery. Nearly 140 women in that group had moderately preterm births.

Researchers determined there was no significant association between a history of bariatric surgery and very preterm births, completing less than 32 weeks of pregnancy. These births occurred in 24 of the 1,941 women in the surgery group and 78 of the 6,574 in the control group, or about 1 percent for both groups.

Study authors said significantly higher risk of spontaneous preterm birth was found, but not medically indicated preterm birth among the women who had bariatric surgery.

The study findings indicated preterm births occurred in 8 percent of women who underwent bariatric surgery less than a year before becoming pregnant. About 10 percent of women who conceived between 1 to 2 years after surgery experienced preterm births and 8 percent of women who waited more than 2 years after surgery before becoming pregnant had preterm births.

Obesity is considered a risk factor for preterm birth, yet researchers “found a significant inverse association between obesity after bariatric surgery and the risk of preterm birth.”

Often many women who are obese have difficulty conceiving and doctors recommend they lose weight to increase their chances of conceiving. Many obese women will then turn to bariatric surgery as an effective and often permanent way to lose the weight and increase their chances of having a baby.

Other research has indicated patients who opt for weight loss surgery face side effects and other complications from the surgery. A study published in 2016 indicated patients who underwent bariatric surgery faced an increased risk of suffering bone fractures both before and after surgery.

A prior study conducted by this same team found conflicting results, bariatric surgery had no effect on preterm birth. However, that study only focused on 600 women and was conducted during a shorter study period. Another study conducted at the same University concluded women who underwent bariatric surgery had a higher risk of preterm birth and having babies that were smaller than normal.

“In contrast to the findings reported in our earlier article, we now report a significant association between a history of bariatric surgery and an increased risk of preterm birth and spontaneous preterm birth in particular,” wrote study authors.