During pregnancy, intestinal obstruction due to sigmoid volvulus is extremely rare. Only 73 cases have been reported. A 24-year-old black woman, gravida 2, para 1, presented during Week 36 of an otherwise uneventful pregnancy, with intermittent abdominal pain and constipation, and no history of nausea, vomiting, fever, chills, previous medical problems, or prior abdominal surgery. Her previous pregnancy was a spontaneous vaginal delivery of a normal full-term neonate. On examination, she was afebrile, with abdominal tenderness. Laboratory studies revealed elevated WBC count of 13,500. She was admitted and given a Fleet enema, with no result or change in abdominal pain. Pain worsened; reexamination of her cervix revealed 3 cm dilation. After Pitocin augmentation, a viable male infant with Apgars of 7 and 9 was delivered. Postpartum, abdominal pain continued, with worsening abdominal distention. Radiograph revealed a massively distended colon. Physical examination 12 hours postdelivery indicated peritonitis. Exploratory laparotomy revealed volvulated, gangernous, massively distended sigmoid colon. The sigmoid colon was resected and Hartmann's colostomy performed. She was discharged on postoperative Day 4. Sigmoid volvulus complicating pregnancy is an uncommon and potentially devastating development that should be suspected with worsening abdominal pain and evidence of bowel obstruction. Prompt intervention is necessary to minimize maternal and fetal morbidity.