A 32-year-old G2P1 at 34 weeks of gestation presents with acute onset of abdominal pain and vaginal bleeding. Obstetric examination shows the uterus is tense and tender. Fetal heart rate is 110 bpm with variable decelerations. Ultrasound reveals a transverse lie with the fetal back anterior, placenta on the anterior wall, and a small amount of free fluid in the pelvis. There is no history of previous cesarean section. What is the most likely diagnosis and the most appropriate immediate management?