When should prophylactic antibiotics be administered before a cesarean section (C-section)?

Timing of Prophylactic Antibiotics for Cesarean Section

Prophylactic antibiotics should be administered 30-60 minutes before skin incision (Option B: before 60 minutes), not after cord clamping. 1, 2

Evidence-Based Recommendation

The Enhanced Recovery After Surgery (ERAS) Society guidelines explicitly recommend administering prophylactic antibiotics 30-60 minutes before skin incision for cesarean delivery. 1 This timing represents a significant shift from the historical practice of administering antibiotics after umbilical cord clamping, which was based on outdated concerns about neonatal antibiotic exposure. 1

Why Pre-Incision Administration is Superior

Pre-incision antibiotic administration significantly reduces maternal infectious morbidity compared to post-cord clamping administration: 3

• Composite maternal infectious morbidity reduced by 43% (RR 0.57,95% CI 0.45-0.72) 3
• Endometritis reduced by 46% (RR 0.54,95% CI 0.36-0.79) 3
• Wound infection reduced by 41% (RR 0.59,95% CI 0.44-0.81) 3
• No increase in neonatal sepsis (RR 0.76,95% CI 0.51-1.13) 3

This high-quality Cochrane systematic review of 5,041 women provides definitive evidence that pre-incision administration is superior for maternal outcomes without harming neonates. 3

Specific Timing Protocol

The optimal window is 30-60 minutes before skin incision: 1, 2, 4

• Antibiotics must be given at least 30 minutes before incision to ensure adequate tissue levels 2
• Administration should be completed by 60 minutes before surgery 2, 5
• This timing ensures therapeutic antibiotic concentrations are present in serum and tissues at the moment of initial surgical incision 1, 5

First-Line Antibiotic Regimen

Cefazolin 2g IV is the recommended prophylactic antibiotic: 2

• Standard dose: 2g IV for BMI <30 kg/m² 2
• Higher dose: 3g IV for BMI ≥30 kg/m² 2
• Single dose is sufficient for procedures <4 hours 2

For women in labor or with ruptured membranes, add azithromycin 500mg IV to the cefazolin regimen for additional reduction in postoperative infections. 2 This combination reduces endometritis rates to extremely low levels (1.3%) compared to cefazolin alone after cord clamping (16.4%). 6

Clinical Pitfalls to Avoid

Common mistake: Delaying antibiotics until after cord clamping 1, 3

• This outdated practice was based on theoretical concerns about neonatal antibiotic exposure that have been disproven 3
• No evidence shows increased neonatal sepsis evaluations or proven sepsis with pre-incision administration 3, 6

Timing error: Administering too close to incision 1

• Antibiotics given <30 minutes before incision may not achieve adequate tissue levels 2
• The drug needs time to distribute into surgical tissues before bacterial contamination occurs 1

Answer to Your Question

The correct answer is B: before 60 minutes. More specifically, antibiotics should be given in the 30-60 minute window before skin incision. 1, 2 Option A (before 30 minutes) would be too close to the incision time and may not allow adequate tissue penetration, while waiting until after cord clamping (the old practice) significantly increases maternal infectious complications. 3