Bariatric surgery pre-conception may reduce birth defects

Among women with severe obesity, undergoing bariatric (Roux-en-Y gastric bypass) surgery prior to conception was associated with a reduced risk of major birth defects in their infants, according to a matched cohort study conducted in Sweden.

Using the Swedish Medical Birth Register, the researchers identified singleton infants born between 2007 and 2014 to women who, based on the Scandinavian Obesity Surgery Register, had undergone Roux-en-Y gastric bypass surgery over the same time frame (n=2,921; mean BMI pre-surgery 43.5 kg/m², mean weight pre-surgery 122 kg). The infants were matched with singleton infants born over the same period to women who had not undergone bariatric surgery (n=30,573).

Mean maternal age was 31 years in both groups and 41 and 38 percent of women who did and did not undergo bariatric surgery were primiparous. A majority of the women (40 percent) had a body mass index (BMI) of 40–44.9 kg/m² while 24 percent had a BMI of 35–39.9 kg/m². Fifteen and 14 percent of women who did and did not undergo bariatric surgery were smokers. Of the parous women, 3.9 and 3.6 percent, respectively, had a history of major birth defects. The median time between surgery and conception was 1.6 years.

The risk of major birth defects was significantly reduced among infants born to women who had undergone bariatric surgery compared with those who had not undergone surgery (3.4 percent vs 4.9 percent; risk ratio [RR], 0.67, 95 percent confidence interval [CI], 0.52–0.87; p=0.002). [JAMA 2019;322:1515-1517]

The primary birth defect in infants born post-bariatric surgery was major heart defects (60 percent). None of the infants born after bariatric surgery had neural tube defects compared with 20 incidents in the non-surgery group.

The reduced risk of major birth defects following bariatric surgery was consistent in a sensitivity analysis that excluded infants with chromosomal abnormalities (3.2 percent vs 4.8 percent; RR, 0.66, 95 percent CI, 0.51–0.85; p=0.001).

Previous studies have shown an association between poor pre- or post-conception glycaemic control or maternal obesity and subsequent birth defects in infants. [BMJ 2018;362:k2638; BMJ 2017;357:j2563]

In the present study, mean weight loss was 40 kg in the surgery group and the use of anti-diabetes medication reduced from 9.7 percent pre-surgery to 1.5 percent 6 months before conception.

“If the observed association is true, 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 (3.5 percent),” said the authors.

The results also suggest that folate-deficiency, thought to be an outcome of bypass surgery and potentially leading to neural tube defects, [World J Diabetes 2017;8:464-474] did not affect the infants in this study.

“This study shows that weight loss and improved blood sugar control in the mother can actually result in a lower risk of birth defects in the child,” said study author Professor Martin Neovius from the Department of Medicine (Solna), Karolinska Institutet, Stockholm, Sweden. “It should help reduce fears that bariatric surgery increases the risk of birth defects in the event of future pregnancy, assuming that surgery patients take their recommended nutritional supplements.”

“[I]t is important that these women receive special antenatal care, including additional ultrasounds to monitor fetal growth and detailed nutritional counselling that includes administration of supplements necessary after weight-loss surgery. Antenatal care providers should also check for nutrition deficiencies in addition to iron, such as folic acid, calcium, and vitamin B12,” added co-author Dr Olof Stephansson from the same institution.