Q. A 19-year-old primigravida at 35 weeks gestation comes to the emergency room for vaginal discharge of blood-stained mucus along with abdominal cramping since morning. Her temperature is 98.4°F (36.9°C), pulse is 80/min, blood pressure is 120/86 mmHg, and respirations are 14/min. Physical examination is consistent with 35 weeks of gestation. The fetal heart tracing shows a rate of 150/min without decelerations. A tocometer detects uterine contractions every 10 minutes lasting 30 seconds each. A sterile vaginal examination shows a cervical dilation of 5cm and a moderate amount of blood-stained mucus. What is the most probable diagnosis in this patient?