A 28-year-old primigravida at 32 weeks of gestation presents to the emergency department with complaints of vaginal bleeding and lower abdominal pain for the past 4 hours. On examination, her blood pressure is 130/85 mmHg, pulse 102/min, and temperature 37.2°C. The uterus is tender on palpation with frequent uterine contractions (6 contractions in 10 minutes). Speculum examination shows blood in the vagina but no cervical lesions. Fetal heart rate is 145 bpm. Ultrasound shows a normally positioned placenta with no evidence of placental abruption. Cervical length on transvaginal ultrasound is 2.8 cm. What is the most appropriate immediate management?