Q. A 32-year-old woman, G2P1 at 38 weeks of gestation comes to the hospital for the trial of labor after a previous cesarean section. Her temperature is 98.4°F (36.9°C), pulse is 90/min, blood pressure is 120/80 mmHg, and respirations are 14/min. Physical examination is consistent with 38 weeks of gestation and fetal heart rate is 150/min. The labor is induced with oxytocin. After a few hours, the patient complains of a sudden increase in abdominal pain, and vaginal bleeding and asks for more epidural anesthesia. Her pulse is 110/min and blood pressure is 90/60 mm of Hg. On physical examination, her abdomen is tender and tense with guarding. The fetal heart rate shows 90/minute. The cervix is fully dilated. The fetal head which was at -1 station, is now floating. External tocodynamometry shows increased uterine contractility and loss of uterine tone. What is the most likely diagnosis?