What does antibiotic administration in a mother with preterm premature rupture of membranes (PPROM) for 4 hours without fever primarily prevent in the neonate?

Antibiotic Administration in PPROM Primarily Prevents Neonatal Sepsis

The correct answer is B - Sepsis. Antibiotics administered to mothers with PPROM primarily prevent neonatal sepsis and other infectious complications, not respiratory distress syndrome (RDS). 1, 2

Primary Mechanism: Prevention of Vertical Transmission and Infection

• Antibiotics reduce vertical transmission of bacteria from mother to neonate, directly preventing early-onset neonatal sepsis as the primary mechanism of benefit 1
• The landmark NICHD trial demonstrated that antibiotic therapy significantly reduced neonatal sepsis within 72 hours of birth (8.4% vs 15.6% in GBS-negative women, p=0.01) 2
• Neonatal infection overall was reduced by 32% with antibiotic use (RR 0.68,95% CI 0.53 to 0.87) 3

Why Not RDS?

The examinee's reasoning about "latency antibiotics increasing lung maturation" reflects a misunderstanding of the mechanism:

• Antibiotics do prolong pregnancy latency (delivery delayed beyond 48 hours: RR 0.71; beyond 7 days: RR 0.80), but this is a secondary effect, not the primary preventive mechanism 2, 3
• While longer latency theoretically allows more time for fetal lung development, antibiotics themselves do not directly cause lung maturation - that requires corticosteroids 2
• The reduction in RDS seen with antibiotics (40.5% vs 48.7%, p=0.04) is likely mediated through reduced infection and inflammation, not direct lung maturation 2
• The primary outcome prevented is sepsis and infectious morbidity, not RDS 1, 2

Evidence Supporting Sepsis Prevention as Primary Benefit

• Maternal chorioamnionitis was reduced by 43% (RR 0.57,95% CI 0.37 to 0.86) 3
• Neonatal pneumonia was reduced (2.9% vs 7.0%, p=0.04) in the antibiotic group 2
• Necrotizing enterocolitis was reduced (2.3% vs 5.8%, p=0.03) with appropriate antibiotic regimens 2
• Duration of antibiotic exposure ≥4 hours before delivery directly correlates with reduction in neonatal colonization and infection risk 1

Clinical Context of the Question

In a patient with PPROM for only 4 hours:

• The 4-hour timeframe is specifically relevant for GBS prophylaxis effectiveness - antibiotics given ≥4 hours before delivery are highly effective at preventing vertical GBS transmission and early-onset GBS disease 1
• At 4 hours, the primary concern is preventing ascending infection and vertical transmission to the neonate 1
• The absence of fever does not eliminate infection risk, as subclinical infection is common with PPROM 3

Recommended Antibiotic Regimen

• Standard regimen: IV ampicillin 2g every 6 hours plus erythromycin 250mg every 6 hours for 48 hours, followed by oral amoxicillin 250mg every 8 hours plus erythromycin 333mg every 8 hours for 5 additional days (7-day total course) 1, 4, 5, 2
• This regimen provides comprehensive coverage against the polymicrobial pathogens causing chorioamnionitis and neonatal sepsis 6
• Avoid amoxicillin-clavulanic acid due to increased necrotizing enterocolitis risk (RR 4.60,95% CI 1.98 to 10.72) 1, 4, 3

Common Pitfall Highlighted by This Question

The misconception that "latency antibiotics" work primarily through prolonging pregnancy for lung maturation is incorrect. The name refers to prolonging the latency period (time from rupture to delivery), but the primary neonatal benefit is infection prevention, not respiratory maturation 1, 2, 6