A 32-year-old multigravida (G3P2) at 30 weeks of gestation presents with regular uterine contractions occurring every 5–7 minutes for the past 3 hours, associated with vaginal spotting. She has a history of preterm delivery at 34 weeks in her second pregnancy. On examination, vital signs are normal. Cervical examination reveals 80% effacement and 3 cm dilation. Fetal heart rate is 142 bpm with normal variability. Ultrasound confirms a singleton gestation with cephalic presentation and estimated fetal weight 1400 g. Vaginal culture from a previous visit (2 weeks ago) was positive for Group B Streptococcus. What is the most appropriate immediate intervention?