Timing of Preoperative Antibiotic Administration in PPROM Before Cesarean Section
Administer intravenous cefazolin 30-60 minutes before skin incision (Answer: B - 60 minutes before incision, though 30 minutes is also acceptable). This timing ensures therapeutic antibiotic concentrations are achieved in maternal tissues before bacterial contamination occurs during surgery, reducing the risk of postoperative infections in women with PPROM 1, 2.
Recommended Timing Window
The ERAS Society and ACOG both recommend antibiotic administration within 60 minutes before the cesarean delivery skin incision, with the optimal window being 30-60 minutes prior to surgery 1, 2.
The FDA label for cefazolin specifies administration 1/2 hour to 1 hour (30-60 minutes) prior to the start of surgery to ensure adequate antibiotic levels are present in the serum and tissues at the time of initial surgical incision 3.
This pre-incision timing represents a shift from historical practice of administering antibiotics after cord clamping, as current evidence demonstrates that pre-incision administration decreases wound infections without causing fetal harm 1.
Rationale for This Specific Timing
PPROM represents a higher-risk scenario, classified as a clean-contaminated (class II) or potentially contaminated (class III) incision, carrying increased risk from both skin flora and vaginal flora exposure 1, 2.
Pharmacokinetic studies demonstrate that cefazolin clearance increases during pregnancy, and the distribution volume is approximately 9.44 liters with pre-delivery clearance of 7.18 liters/hour 4.
Computer simulations reveal that the probability of maintaining free cefazolin concentrations above 8 mg/liter during cesarean surgery is less than 50% in cord blood when cefazolin is administered less than 1 hour before delivery 4.
Recommended Antibiotic Regimen for PPROM
Administer cefazolin 2g IV as the primary antibiotic, with the addition of azithromycin for women with ruptured membranes, as this combination confers additional reduction in postoperative infections beyond cephalosporin alone 1, 2.
The combination provides broader coverage against potential pathogens in the setting of membrane rupture, which increases infection risk 2.
Important Clinical Considerations
Do not delay antibiotic administration until after cord clamping in the setting of PPROM, as this outdated practice increases maternal infection risk without providing fetal benefit 1.
A randomized controlled trial demonstrated that cefazolin administered before skin incision versus after cord clamping both significantly reduced postoperative infectious morbidity compared to placebo (4.9% and 3.8% versus 12.1%, p<0.001), with no significant difference between the two cefazolin timing groups 5.
For procedures lasting longer than 4 hours, consider an additional intraoperative dose of cefazolin 1g 2.