Review Question - QID 109128

A 29-year-old G2P2 woman gives birth to a healthy baby boy at 39 weeks of gestation via vaginal delivery. Immediately after the delivery of the fetus, she experiences profuse vaginal hemorrhage as the physicians attempt to deliver the placenta. Her prior birthing history is notable for an emergency cesarean section during her first pregnancy. She did not receive any prenatal care during either pregnancy. Her past medical history is notable for obesity and diabetes mellitus, which is well controlled on metformin. Her temperature is 99.0°F (37.2°C), blood pressure is 95/50 mmHg, pulse is 125/min, and respirations are 22/min. On physical examination, the patient is in moderate distress. Her extremities are pale, cool, and clammy. Capillary refill is delayed. Which of the following is the most likely cause of this patient’s bleeding?