A 32-year-old primigravida at 34 weeks gestation presents to the emergency department with sudden onset of severe abdominal pain and vaginal bleeding. She reports a history of hypertension (BP 160/100 mmHg currently) and denies any recent trauma. On examination, the uterus is tender and woody hard. Fetal heart rate is 90 bpm (baseline 140 bpm). Ultrasound shows a retroplacental clot measuring 4 cm × 3 cm. Her hemoglobin is 9.2 g/dL (baseline 11.5 g/dL), and coagulation profile shows PT 16 s, aPTT 42 s, fibrinogen 120 mg/dL, and D-dimer markedly elevated. What is the most appropriate immediate management?