Bariatric surgery linked to premature birth and small birthweight

by Bruce Sylvester – Women who have undergone bariatric surgery are more likely to give birth to premature babies and to babies who are small for gestational age, researchers reported in the British Medical Journal on Nov. 12, 2013.  

The study, the most extensive ever performed on the subject, used data from the Swedish Medical Birth Register and the Patient Register.

“Mothers with the same BMI gave birth to babies of varying weights depending on whether or not they had undergone bariatric surgery, so there is some kind of association between the two,” said Dr. Olof Stephansson, obstetrician and Associate Professor at the Clinical Epidemiology Unit at Karolinska Institutet in Stockholm. “The mechanism behind how surgery influences fetal growth we don’t yet know, but we do know that people who have bariatric surgery are at increased risk of micronutrient deficiencies.”

The investigators compared data from over 2,500 babies born to women who had previously undergone bariatric surgery with data from 12,500 babies born to mothers who had not had bariatric surgery. Pregnancies were carefully matched between the groups for mothers’ BMI, age, educational background, smoking habits, and previous births.

The investigators reported that newborns of women with bariatric surgery history had lower birth weights; 5.2 per cent were small for gestational age compared to 3.0 per cent in the control group.

Also, 4.2 per cent of the babies of mothers with bariatric surgery history were large for gestational age, compared to 7.3 per cent of the control group.

More were born prematurely in the bariatric surgery history group, at 9.7 per cent before the 37th week, compared with 6.1 per cent of the control group.

The researchers reported no difference in rate of stillbirth or neonatal death (within the first 27 days) between the groups.

They concluded that women with bariatric surgery history are an at-risk group when pregnant, and they should get close prenatal attention, extra ultrasound to check fetal growth and special dietary supplement recommendations.

They also noted that bariatric surgery has benefits for mothers, like lowering the risk of diabetes, cardiovascular disease, cancer and stroke..