To determine the incidence and clinical characteristics of surgical complications during pregnancy in women with a history of bariatric surgery.

A nationwide, prospective, population-based cohort study.

High-risk obstetric care in Belgium: 67.6% of maternity units participated, covering 65% of all births in the study period.

Pregnant women with a history of bariatric surgery presenting with a surgical complication (internal hernia, intussusception, volvulus or adhesions; anastomotic ulcer or abscess; gastric band slippage or incisional hernia) between January 2021 and December 2022.

33 women experienced 35 surgical complications. Internal herniation was most common (n=25), predominantly following Roux-en-Y gastric bypass. Mean gestational age at diagnosis was 27+6 weeks. All women underwent surgical exploration within 24 hours; bowel resection was required in two cases. Caesarean section occurred in 48.5%, with 13 preterm births and one neonatal death. One woman required intensive care. No maternal death occurred.

Surgical complications following bariatric surgery in pregnancy are uncommon but carry significant obstetric risks. In this cohort, all reported complications occurred after procedures involving intestinal rerouting, predominantly Roux-en-Y gastric bypass. Prompt surgical management was associated with low maternal morbidity and no mortality, but frequently resulted in preterm birth and emergency caesarean section. These findings highlight the need for a low threshold for surgical evaluation of abdominal pain in pregnant women with previous bariatric surgery and support balanced counselling regarding the potential benefits and risks of different bariatric procedures in women of reproductive age.