Timing of Preoperative Antibiotic Administration in PPROM with Cesarean Section
Antibiotics should be administered 30-60 minutes before skin incision (Answer A or B), with the optimal window being within 60 minutes prior to incision. 1
Recommended Timing and Rationale
The American College of Obstetricians and Gynecologists explicitly recommends administering cefazolin 2g IV within 60 minutes before skin incision for cesarean section prophylaxis. 1 This timing applies to all cesarean sections, including those performed in women with PPROM. 1
The FDA labeling for cefazolin specifies administration "1/2 hour to 1 hour prior to the start of surgery" for perioperative prophylaxis, which translates to 30-60 minutes before incision. 2 This timing ensures adequate antibiotic levels are present in serum and tissues at the time of initial surgical incision. 2
Key Evidence Supporting Pre-Incision Timing
Administration before skin incision is superior to administration after cord clamping. A meta-analysis demonstrated that prophylactic cefazolin given before skin incision significantly reduced the risk of surgical site infection compared to administration after umbilical cord clamping (OR 0.48,95% CI 0.29-0.82). 3
A randomized controlled trial comparing cefazolin before incision versus after cord clamping versus placebo found no significant difference in infectious morbidity between the two cefazolin timing groups (4.9% vs 3.8%, p=0.60), but both were superior to placebo (12.1%, p<0.001). 4 This supports that either timing within the pre-incision window is acceptable, but current guidelines favor pre-incision administration. 1
Special Considerations for PPROM
For women with PPROM undergoing cesarean section, the standard cefazolin 2g IV dose should be supplemented with azithromycin to provide broader coverage and further reduce postoperative infections. 1 This combination is specifically recommended by the American College of Obstetricians and Gynecologists for women with prolonged rupture of membranes, as cesarean delivery in this setting is classified as clean-contaminated (class II) with higher infection risk. 1
Practical Implementation
The mean time from drug administration to incision in clinical practice is approximately 13 minutes, which falls well within the recommended 30-60 minute window. 5
Cefazolin concentrations remain above the minimal inhibitory concentration (MIC) for susceptible pathogens throughout the procedure when given 30-60 minutes before incision. 5, 6
If the cesarean procedure extends beyond 4 hours, an additional 1g dose of cefazolin should be considered. 1
Common Pitfall to Avoid
The outdated practice of administering antibiotics after cord clamping (to theoretically reduce neonatal antibiotic exposure) should be abandoned, as pre-incision administration provides superior maternal protection without clinically significant neonatal harm. 1, 3
Answer: A (30 minutes before incision) or B (60 minutes before incision) are both correct, as the guideline-recommended window is 30-60 minutes before skin incision.