What antibiotics are used for a pregnant woman with preterm ruptured membranes (PROM)?

Antibiotics for Preterm Premature Rupture of Membranes (PPROM)

The correct answer is C (ampicillin), which is the cornerstone antibiotic for PPROM, typically combined with erythromycin as the standard evidence-based regimen. 1, 2, 3

Standard Antibiotic Regimen

The recommended protocol for PPROM at ≥24 weeks gestation consists of: 2, 3, 4

• IV ampicillin 2g every 6 hours PLUS erythromycin 250mg IV every 6 hours for 48 hours
• Followed by oral amoxicillin 250mg every 8 hours PLUS erythromycin 333mg orally every 8 hours for 5 additional days (total 7-day course)

This regimen has GRADE 1B evidence (strong recommendation) for prolonging pregnancy latency, reducing maternal infection and chorioamnionitis, and decreasing neonatal morbidity. 2, 3, 4

Why Each Answer Choice Matters

Ampicillin (C) - CORRECT

• Ampicillin is the primary antibiotic recommended by ACOG and CDC guidelines 1, 2, 3
• Significantly reduces maternal chorioamnionitis (odds ratio 0.52) 5
• Reduces Grade 3/4 intraventricular hemorrhage (RR 0.42) 6
• Provides GBS prophylaxis for preterm delivery <37 weeks 1

Clindamycin (B) - AVOID as monotherapy

• Clindamycin alone increases the risk of maternal infection and should NOT be used as monotherapy 5
• Only effective when combined with gentamicin (clindamycin + gentamicin reduces chorioamnionitis with OR 0.16) 5, 6
• Not part of standard PPROM protocols 2, 3

Metronidazole (D) - NOT recommended

• Metronidazole is not included in evidence-based PPROM antibiotic regimens 2, 3, 4
• While one local study from Nigeria suggested metronidazole combinations, this contradicts major guideline recommendations 7
• No high-quality evidence supports its routine use in PPROM

Vancomycin (A) - NOT standard therapy

• Vancomycin is not part of standard PPROM antibiotic protocols 2, 3, 4
• Reserved only for specific situations (e.g., MRSA colonization, severe penicillin allergy with high anaphylaxis risk)

Alternative Regimens

If erythromycin is unavailable: 2

• Azithromycin can substitute for erythromycin

For penicillin-allergic patients without anaphylaxis risk: 1

• Cefazolin for GBS prophylaxis

For penicillin-allergic patients: 4

• Erythromycin 250mg orally every 6 hours for 10 days alone (macrolide monotherapy)

Critical Pitfalls to Avoid

Never use amoxicillin-clavulanic acid (Augmentin) - this combination significantly increases the risk of necrotizing enterocolitis in neonates. 1, 2, 3, 4 Note that amoxicillin WITHOUT clavulanic acid is safe and recommended. 4

Do not delay antibiotic administration - antibiotics should be started promptly when PPROM is diagnosed at ≥24 weeks gestation. 1, 3

Avoid prolonged or repeated antibiotic courses beyond the standard 7-day regimen to optimize antibiotic stewardship. 2

Gestational Age Considerations

• ≥24 weeks: Strong evidence (GRADE 1B) for antibiotic use 2, 3, 4
• 20-23 6/7 weeks: Antibiotics may be considered but evidence is weaker (GRADE 2C) 2, 3
• <20 weeks: Insufficient evidence for routine antibiotic use 2

Additional Management Points

Beyond antibiotics, monitor for signs of chorioamnionitis: 2, 3

• Maternal fever ≥38°C
• Maternal or fetal tachycardia
• Uterine tenderness
• Purulent cervical discharge

Important caveat: Infection may present without maternal fever, especially at earlier gestational ages, so maintain high clinical suspicion. 2, 3