Published: 24-08-2016 23:00 | Updated: 26-08-2016 09:01

Obesity surgery increases the risk of preterm birth

Babies of women who have undergone bariatric surgery for obesity run a higher risk of preterm birth, according to a new study from Karolinska Institutet published in The New England Journal of Medicine.

Obesity in pregnant women increases the risk of complications that can adversely affect the health of both mother and child. For example, there is a higher chance of preterm delivery than in women of normal weight. With the rising popularity of bariatric surgery, which leads to substantial and often permanent weight loss, the number of women receiving surgery for obesity prior to having a baby has increased dramatically in Sweden and around the world.

Increased risk

“Since obesity is associated with a higher risk of preterm delivery, we assumed that the weight-loss achieved by surgery would reduce this risk, especially as it also reduced the risk of gestational diabetes,” says research team member Olof Olof Stephansson Foto: Anneli MiltonStephansson from Karolinska Institutet’s Department of Medicine, Solna. “Instead, we found that it increased the risk.”

Using data from the Scandinavian Obesity Surgery Registry (SOReg) and National Swedish Health Registers, the researchers found almost 2,000 babies born of post-bariatric surgery women between 2006 and 2013 and compared them with the babies of 6,500 women who had not been operated on but who had the same BMI as the first group prior to surgery.

They found that the women who had undergone surgery ran a higher risk of preterm delivery (i.e. before week 37), so that while 6.8 per cent of the control group had premature babies, the corresponding figure in the surgery group was 8.4 per cent.

“Since bariatric surgery followed by pregnancy can increase the risk of preterm birth, such women ought to be considered risk pregnancies and should receive particular care and attention from the maternity care services,” says Dr Stephansson. “This means, for instance, giving them extra ultrasound scans to check fetal growth and detailed dietary advice that includes the supplements they need after bariatric surgery. They should also be checked for any possible nutrient deficiencies other than iron.”

Positive effects

Bariatric surgery can also have positive effects on subsequent pregnancies. In earlier studies, the Dr Stephansson’s group found that surgery reduces the risk of gestational diabetes and was associated with normalised birth size. The earlier study suggested that bariatric surgery increased the risk of premature birth but the difference was not statistically significant. Since bariatric surgery has now become so popular, the researchers in the present study were able to follow a much larger group of women and thus confirm this suspected correlation between surgical intervention and preterm birth.

The study was financed by the Swedish Research Council and the National Institutes of Health, USA.


Bariatric surgery and preterm birth
Olof Stephansson, Kari Johansson, Ingmar Näslund and Martin Neovius
The New England Journal of Medicine, published online 25 August 2016, doi: 10.1056/NEJMc1516566