Bariatric surgery can increase risk of preterm birth

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

“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,” said research team member Olof Stephansson from Karolinska Institutet’s Department of Medicine, Solna. “Instead, we found that it increased the risk.”

In the correspondence letter to the journal, ‘Bariatric Surgery and Preterm Birth’, the researchers state that they used data from the Scandinavian Obesity Surgery Registry (SOReg) and National Swedish Health Registers, and 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,” said Stephansson. “This means, for instance, giving them extra ultrasound scans to check foetal 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.”

Bariatric surgery can also have positive effects on subsequent pregnancies. In earlier studies, the Stephansson’s group found that surgery reduces the risk of gestational diabetes and was associated with normalised birth size. The earlier study, Outcomes of Pregnancy after Bariatric Surgery’, 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.

“In contrast to the findings reported in our earlier article, we now report a significant association between a history of bariatric surgery and an increased risk of preterm birth and spontaneous preterm birth in particular,” they write. “Despite careful matching, differences between the surgery group and the control group may have influenced the results.”

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