The occurrence of ectopic decidua has been observed mostly in the ovaries, uterus and cervix. Ectopic gastrointestinal deciduosis is a physiological condition. Only several cases of ectopic decidua, causing complications have been presented in literature. To the best of our knowledge, sigmoid or any other bowel perforation, caused by deciduosis, has not been previously reported in literature.Case presentation: A 40-year old patient primigravida (32 weeks of gestation) was admitted with a severe abdominal pain and obstipation. An abdominal sonography was performed but no visual cause of the pain was diagnosed. Two days after admission the episode of severe pain reappeared. An abdominal sonography and x-ray showed "free air" under both domes of diaphragm. A laparotomy was performed. No perforation of hollow viscus was found. On the fifth postoperative day, the patient started to complain about acute abdominal pain. The decision was made to perform relaparotomy (a Caesarean section and reexploration of abdominal cavity during the same operation). During the relaparotomy a part of sigmoid colon was visually altered. A microperforation on tumour-like structures was found in the sigmoid colon. A Sigmoid resection was performed. Currently the patient has no residual complaints and is enjoying her motherhood. Conclusion:We assert that ectopic decidua can result in a perforation of the hollow viscus, which is a lifethreatening condition and should always be taken into account seriously. We believe that sigmoid microperforation could have found, we had taken a more aggressive approach and performed a Caesarean section during the first operation.