(HealthDay News) – Women with a history of bariatric surgery are at increased risk for preterm or small-for-gestational-age babies, according to a study published online Nov. 12 in BMJ.

Nathalie Roos, PhD, from the Karolinska Institutet in Stockholm, and colleagues compared perinatal outcomes in births of women with a history of bariatric surgery (2,562 birth) vs.  those without (up to five matched controls for each birth) identified from the Swedish medical birth register (between 1992 and 2009).

The researchers found that there were significantly more preterm births after surgery than in matched controls (9.7% vs. 6.1%; odds ratio, 1.7). The effect was modified by body mass index (BMI; P=0.01), and the elevated preterm birth risk was only seen in women with BMI <35kg/m². The risks of spontaneous and medically indicated preterm birth were increased with a history of bariatric surgery (odds ratios, 1.5 and 1.8, respectively). The risk of a small-for-gestational-age birth was increased (odds ratio, 2) and the risk of a large-for-gestational-age birth was decreased (odds ratio, 0.6) with a history of bariatric surgery. There were no differences observed in the risks of stillbirth or neonatal death.

“Women with a history of bariatric surgery were at increased risk of preterm and small-for-gestational-age births and should be regarded as a risk group during pregnancy,” the authors conclude.

One author disclosed financial ties to the pharmaceutical industry and compensation for obesity work.

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