An ectopic pregnancy developing in a previous cesarean section scar is an extreme rarity among all ectopic pregnancies. Due to the difficulty of making an accurate diagnosis, this kind of ectopic pregnancy is the most dangerous and life-threatening type. A 30-year-old woman, who was gravida 4, para 3, was admitted to our emergency room with massive vaginal bleeding. She had undergone a cesarean section due to a breech birth 3 months prior to this admission. Ultrasound examination showed a pregnancy located in the low corpus uterus. The possibility of a spontaneous abortion in progress or a cervico-isthmic pregnancy were considered. Due to the massive vaginal bleeding and unstable vital signs of the patient, surgical intervention was decided upon to save the woman's life. We first performed dilatation and curettage. There was no gestational villi and severe vaginal bleeding was noted during this procedure. An emergent exploratory laparotomy was then performed, followed finally by a hysterectomy. Pathologic findings confirmed the diagnosis of a pregnancy in the previous cesarean section scar. Diagnosis, prevention, clinical evaluation and management of these conditions are discussed.