Q. A 32-year-old gravida 2 para 1 woman at 34 weeks of gestation comes to the emergency department for a sudden onset of severe abdominal pain accompanied by mild vaginal bleeding. She characterizes the pain as persistent and sharp. She reports no history of trauma or drug use. Her first pregnancy was without any complications. Until this incident, her current pregnancy has been uneventful. On examination, her vital signs include a blood pressure of 145/90 mmHg and a pulse of 110 beats per minute. Her abdominal examination shows tenderness and a notably rigid uterus. Fetal monitoring shows a heart rate of 140 beats per minute and uterine contractions with high frequency and low amplitude. What is the most probable explanation for her symptoms?