In Denmark, the number of bariatric operations, including gastric bypass surgery, has increased dramatically in recent years. Internal herniation as a possible cause of acute abdominal pain, is a well-known complication after gastric bypass operation. We report two cases of internal herniation during pregnancy following gastric bypass operation. The diagnosis of internal herniation can be difficult as radiologic investigations may be inconclusive. Clinical suspicion alone should lead to surgical exploration due to the risks of morbidity and mortality if patients are not diagnosed properly.