What is the optimal timing for administering a dose of antibiotic preoperatively to a pregnant woman with premature premature rupture of membranes (PPROM) undergoing a cesarean section (CS)?

Timing of Preoperative Antibiotic Administration for Cesarean Section in PPROM

Administer prophylactic antibiotics for cesarean section 30-60 minutes before skin incision to ensure therapeutic tissue concentrations are achieved before bacterial contamination occurs. 1

Critical Distinction: Two Separate Antibiotic Indications

You must understand that a pregnant woman with PPROM going to cesarean section requires two distinct antibiotic regimens with different purposes and timing:

1. Latency Antibiotics for PPROM Management

• These should already be completed or ongoing before the patient reaches the operating room 2, 3
• The standard 7-day course consists of 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 2, 3
• This regimen prevents neonatal sepsis and maternal infection during expectant management 2
• Strong recommendation (GRADE 1B) for PPROM at ≥24 weeks gestation 2, 3

2. Surgical Prophylaxis for Cesarean Section

• This is what you administer preoperatively: cefazolin (or appropriate alternative) given 30-60 minutes before skin incision 1, 4
• The standard dose is cefazolin 2g IV (or 3g if patient weighs >120kg) 4
• Timing is critical: antibiotics must be given within the 30-60 minute window before incision to achieve adequate tissue levels at the moment of surgical contamination 1, 4

Enhanced Surgical Prophylaxis in PPROM Context

For cesarean delivery with ruptured membranes, adding azithromycin to cefazolin provides additional reduction in postoperative infections. 1

• The combination of cefazolin plus azithromycin is superior to cefazolin alone when membranes have been ruptured 1
• This addresses the increased infection risk from prolonged membrane rupture (risk increases substantially after 18 hours) 3, 1

Alternative Regimen for Comprehensive Coverage

• If broader coverage is desired for postpartum pelvic infection prevention in the setting of prolonged rupture, clindamycin plus gentamicin provides comprehensive coverage against aerobic gram-negative organisms and anaerobic bacteria 1
• This regimen is particularly relevant when membrane rupture exceeds 24 hours 1

Common Pitfalls to Avoid

• Do not confuse latency antibiotics with surgical prophylaxis - they serve different purposes and have different timing requirements 2, 3, 1
• Do not delay surgical prophylaxis - giving antibiotics too early (>60 minutes before incision) or too late (after incision) reduces effectiveness 1, 4
• Avoid amoxicillin-clavulanic acid in the latency antibiotic regimen due to increased necrotizing enterocolitis risk in neonates 2, 3
• Do not give only the latency antibiotics and assume surgical prophylaxis is covered - the patient still needs appropriate preoperative dosing 1, 4

Practical Algorithm for the Operating Room

1. Verify latency antibiotics were given (should have been started at PPROM diagnosis) 2, 3
2. 30-60 minutes before skin incision: administer cefazolin 2g IV plus azithromycin 500mg IV 1
3. For lengthy procedures (>2 hours): redose cefazolin 1g IV intraoperatively 4
4. Postoperatively: continue latency antibiotic course if not yet completed, plus standard postoperative monitoring 2, 3