Even though women having the surgery are exposed to some risks, the results were better overall, experts agree.
Such findings have major implications for an increasing number of women and children, especially in the United States, where almost a third of pregnant women are obese.
Common problems found in obese women during pregnancy include gestational diabetes, pre-eclampia, and stillbirth. Babies of obese women are more likely to be premature, with either overweight or underweight at birth, birth defects, and potentially becoming obese later in life.
The findings were published in The New England Journal of Medicine.
In the study, researchers from Sweden examined records of 2,832 obese women who delivered their babies between 2006 and 2011, and compared women who had bariatric surgery before getting pregnant against women who did not.
The results show that women who had the surgery were about 30 percent likely to develop gestational diabetes and 40 percent likely to have overweight babies – a condition posing the challenge for the babies of lung and blood problems.
In some categories, however, the results were worse. Women who had surgery had a double risk of having babies too small for their gestational age, an indication there is an increased need for better nutrition for pregnant women whose stomach was reduced surgically.