Review Question - QID 213699

A 24-year-old G1P0 woman presents to the labor and delivery floor with a 1-hour history of bleeding. She is at 35 weeks of gestation and says that she has had an uneventful pregnancy other than some morning sickness. She realized that she was bleeding at home when she noticed that the chair she was sitting on had fresh red stains. She denies experiencing any fever, chills, pain, or other symptoms. Which of the following is most likely the cause of this patient's symptoms?