Women who have had bariatric surgery appear to be at higher risk of preterm and small for gestational age (SGA) babies, a large study from the Karolinska Institute in Sweden has found. The Swedish birth registry captures data on 98% of all births nationwide. Between 1992 and 2009 more than 1.7 million births were identified, after relevant exclusions, of which 2,562 were to women who had undergone bariatric surgery for obesity, and had a singleton pregnancy.