A 31-year-old woman at 36+2 wk gestation presented to the emergency department with progressive abdominal cramping, nausea and bilious vomiting. The patient’s symptoms started the previous day. She denied fevers, diarrhea, hematochezia and melena. She was treated with intravenous fluids and antispasmodic and analgesic therapy in a local hospital. However, the patient’s symptoms did not significantly improve. Gravidity 2, para 1-0-0-1. A history of left ovarian teratoma resection four years previously, and a new-onset right ovarian teratoma for seven mo. Vital signs were stable. Temperature was 37.2°C, heart rate was 90 bpm, respiratory rate was 24 breaths per minute, and BP was 120/70 mmHg. Abdominal examination revealed tenderness of the bilateral abdomen and subxiphoid area, without rebound tenderness. Fundal height was consistent with gestational age. Leukocytosis of 14.21 × 109/L, neutrophils of 90.0%, D-dimer of 6975 ng/mL, and FIB of 4.64 g/L were observed. The other laboratory examination results were unremarkable. In the emergency department, abdominal ultrasound and gynecological ultrasound examination were performed. Abdominal ultrasound indicated the following: (1) Dilatation of the intestine in the abdominal cavity, with a small amount of peritoneal effusion; (2) No abnormalities were found in the gallbladder and urinary system; and (3) An enlarged appendix was not found. Gynecological ultrasound indicated the following: (1) Fetus was not deformed; and (2) Fetal heart rate was 160 bpm. According to her physical examination and ultrasound results, the patient was suspected to have intestinal obstruction. To determine the cause of intestinal obstruction, an abdominal computed tomography (CT) scan was carried out and the risks to the patient and her family were explained. The CT scan showed that the mesentery was twisted around the SMA resulting in a ‘‘whirlpool’’ sign. The dilated ascending colon had moved to the left abdomen. The transverse colon was located behind the SMA. The above findings suggested that the diagnosis was reverse rotation of the midgut with volvulus.