BACKGROUND: Late complications to bariatric surgery during pregnancy have become an area of concern. Expansion of the uterus and the following displacement of the small intestine may increase the risk of internal herniation. We wanted to estimate the risk and consequences of surgical complications during pregnancy in a national cohort of women with a history of gastric bypass surgery.

METHODS: A national, register-based cohort study of all Danish women with a history of gastric bypass surgery who had given birth from 2004 to 2010 was conducted. Surgical codes registered during pregnancy and until 120 days postpartum were identified in national registers, and the individual charts were reviewed in relevant cases.

RESULTS: Of 286 women giving birth, fourteen women underwent procedures that might be related to the earlier gastric bypass surgery. Three women were operated on suspicion of internal herniation. In all three cases, mesenteric defects were found, and herniation was still present in two women, one of which died postoperatively. Five women were investigated by gastroscopy or sigmoidoscopy either during or after the delivery, and in six women cholecystectomy was performed during the puerperium.

CONCLUSIONS: The incidence of internal herniation during pregnancy was 1 % in our study. Internal herniation may be a serious complication in pregnant women, and both the diagnosis and treatment requires handling by experienced obstetrical, radiological, and surgical staff.