Segmental absence of intestinal musculature (SAM) may, rarely, present with symptoms of ileus or intestinal perforation. Most commonly, the disorder presents with signs of intestinal disorders in newborns. Colonic perforations are then rare in adulthood. In this study, the authors present a case of a young female patient, operated for right abdominal pains when she was 30 weeks pregnant. Although no advanced appendicitis was confirmed, appendectomy was performed. Five days later, surgical revision was indicated for signs of septic condition and abdominal pain. Two perforations of the ascending colon and diffuse peritonitis were found. Section and right-sided hemicolectomy were performed. The final identification of the cause was based on histological examination of the resecate. The perforations were located at the sites, where the intestinal muscular layer was absent. This finding has also got forensic consequences. It revealed a rare cause of colonic perforation, which is undetectable on examination and confirmed that no mistakes were made during the first procedure. The authors did not find any literature data on colonic perforations due to the colonic muscle layer absence during pregnancy.