Weight-loss surgery before pregnancy cuts the risk of birth defects by 30%, says new study
Children born to women who had gastric bypass surgery before becoming pregnant have a 30% lower risk of major birth defects than children born to women who had severe obesity at the start of their pregnancy, say researchers.
The findings, according to the researchers from Karolinska Institutet, Stockholm, Sweden, and Örebro University, Sweden, indicate that weight-loss and improved blood sugar control could reduce the risk of major birth defects and should lessen long-standing concerns that weight-loss surgery could increase this risk.
"Overall, this is a very interesting study as we found that an intervention like bariatric surgery leading to weight loss may influence the prevalence of major birth defects. We can say to mothers that there is no increased risk of birth defects. On the contrary, our study suggests a decreased risk. However, the results from our study have to be confirmed in other settings and by other researchers," Dr. Olof Stephansson, obstetrician and senior researcher at the Department of Medicine (Solna), Karolinska Institutet, and one of the study's main authors, told MEA WorldWide (MEAWW).
According to Dr. Stephansson, major birth defects is a composite outcome of many organ systems, and the most common are heart defects.
"However, the composite outcome includes birth defects from the central nervous system, respiratory, orofacial, digestive, urinary systems, abdominal wall defects, genital organs, and others. We also performed a sub-analysis excluding chromosomal abnormalities from the study with no difference in results," he told MEAWW.
In previous studies, obesity and poor blood sugar control have been linked to an increased risk of health complications for both mothers and their infants. Other studies, say the researchers, have suggested that weight-loss surgery may increase the risk of various nutrient deficiencies, including iron and folate, which are important for fetal development. There have been concerns dating back to the 1980s that bariatric surgery could increase the risk of major birth defects.
"This study shows that weight-loss and improved blood sugar control in the mother can result in a lower risk of birth defects in the child. 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," says Professor Martin Neovius, who is also a researcher at the Department of Medicine in Solna, and one of the study's main authors.
The study was financed by the US National Institutes of Health, the Swedish Research Council and the Swedish Research Council for Health, Working Life and Welfare. The findings have been published in JAMA.
The study findings
In recent years, weight-loss surgery has increased significantly, and about 1.5% of all babies born in Sweden today are delivered by mothers who have had bariatric surgery.
The researchers examined data on more than 33,000 births in Sweden between 2007 and 2014. Of these, 2,921 were children born to mothers who underwent a gastric bypass, and 30,753 were children born to women who weighed about the same as the gastric bypass women did before their surgeries.
The risk of major defects was 3.4% in children born to women who have had gastric bypass surgery, which is in line with the risk of major defects in children born to normal-weight women (3.5%). For women who at their first prenatal checkup had a body-mass index comparable to that of the gastric bypass patients' pre-surgery weight, the risk of major birth defects was 4.9%.
"Major birth defects were recorded in 3.4% of infants born to mothers with gastric bypass surgery versus 4.9% of controls," says the study.
Major heart defects accounted for 60% of birth defects among post-surgery-born infants. "This is what you also find in population controls that the most common major defect is in the cardiovascular system. That said, the study finds that the overall prevalence of major birth defects is decreased, which also accounts for cardiac major heart defects being the most common defects," says Dr. Stephansson.
The women in the surgery group lost an average of 40 kg and weighed around 82 kg at their first prenatal checkup. Their use of diabetes medication decreased from 9.7% to 1.5%.
“In this study, after bariatric surgery, women lost weight and diabetes drug use decreased. 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%),” says the study.
Dr. Stephansson says that while bariatric surgery has many positive effects on pregnancy, it is still important that these women receive special antenatal care. “This includes additional ultrasounds to monitor fetal growth and detailed nutritional counseling that include administration of supplements necessary after weight-loss surgery," he adds.