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?

Explanation

## Clinical Scenario Analysis This patient has **active preterm labor** at 30 weeks (regular contractions with cervical changes) with a history of prior preterm delivery and known GBS colonization. The fetus is viable with reassuring heart rate and normal variability. ## Key Management Principles for Preterm Labor at 30 Weeks **High-Yield:** The triad of management at viable preterm gestation (24–34 weeks) is: 1. **Corticosteroids** — betamethasone or dexamethasone for fetal lung maturity 2. **Tocolytics** — to suppress contractions and gain time for steroid effect 3. **GBS prophylaxis** — intravenous penicillin G or ampicillin if colonized or status unknown ## Rationale for Correct Answer **Betamethasone (12 mg IM × 2 doses, 24 hours apart):** - Reduces respiratory distress syndrome, intraventricular hemorrhage, and neonatal mortality - Most effective between 24–34 weeks - Should be given immediately in preterm labor **Nifedipine (first-line tocolytic):** - Calcium channel blocker; preferred in many centers (especially in India) - Loading dose: 20 mg PO, then 10–20 mg every 4–6 hours - Contraindications: hypotension, cardiac disease - This patient is hemodynamically stable, making it appropriate **Intravenous Penicillin G (or Ampicillin):** - GBS-positive status requires IV antibiotic prophylaxis to reduce vertical transmission and neonatal sepsis - Dosing: Penicillin G 5 million units IV loading, then 2.5–3 million units IV every 4 hours - Ampicillin 2 g IV loading, then 1 g IV every 4 hours (alternative if penicillin unavailable) - Must continue until delivery or rupture of membranes **Clinical Pearl:** GBS prophylaxis is indicated in preterm labor with known colonization because the risk of neonatal sepsis is highest in preterm infants (up to 1 in 200 if untreated). **Mnemonic — STOP-GBS:** Steroids, Tocolytics, Observation, Penicillin (or ampicillin), GBS screening/prophylaxis. ## Why Magnesium Sulfate Is NOT First-Line Here Magnesium sulfate is used for **neuroprotection** (reduces cerebral palsy by ~30%) in preterm labor <32 weeks, but it is NOT a tocolytic. It must be combined with tocolytics (nifedipine, labetalol) and corticosteroids. Using magnesium sulfate alone without tocolytics will not suppress labor. [cite:ACOG Practice Bulletin 127; Williams Obstetrics 26e Ch 42]