Prior maternal gastric bypass surgery tied to fewer birth defects

The risk of major birth defects was lower for infants whose mothers had gastric bypass surgery prior to the pregnancy than it was for infants of matched controls, according to data from a cohort study of 2,921 women with a history of gastric bypass surgery and 30,573 matched controls.

“Obesity is associated with poor glucose control, which is teratogenic. Bariatric surgery results in weight loss and glucose normalization but is also associated with nutritional deficiencies and substance abuse, which could cause birth defects as hypothesized based on case series,” wrote Martin Neovius, PhD, of Karolinska Institutet, Stockholm, Sweden, and colleagues.

To determine the risk of birth defects for infants born to women after gastric bypass surgery, the researchers used the Swedish Medical Birth Register to identify singleton infants born between 2007 and 2014 to women who underwent Roux-en-Y gastric bypass surgery and matched controls. The findings were published in a research letter in JAMA.

In the surgery group, the mean interval from surgery to conception was 1.6 years, and the mean weight loss was 40 kg for these women. In addition, the use of diabetes drugs decreased from 10% before surgery to 2% during the 6 months before conception.

Overall, major birth defects occurred in 3% of infants in the gastric bypass groups versus 5% of infants in the control group (risk ratio, 0.67). No neural tube defects occurred in the surgery group and 20 cases of neural tube defects were noted in the control group.

The study was limited by several factors including the lack of data on pregnancy termination, exclusion of stillbirths, and inability to analyze individual birth defects because of small numbers, the researchers noted.

Nonetheless, the results suggest that “a mechanism could be that surgery-induced improvements in glucose metabolism, and potentially other beneficial physiologic changes, led to a reduction of major birth defect risk to a level similar to that of the general population,” they said.

Dr. Neovius disclosed advisory board fees from Itrim and Ethicon Johnson & Johnson. Three coauthors reported grants or other fees from a variety of pharmaceutical companies. The study was supported by the National Institute of Diabetes and Digestive and Kidney Diseases at the National Institutes of Health, by the Swedish Research Council, and by the Swedish Research Council for Health, Working Life, and Welfare.

SOURCE: Neovius M et al. JAMA. 2019 Oct 15; 322:1515-17.