Which prophylactic antibiotic regimen is recommended to prevent postoperative endometritis after cesarean delivery in a healthy woman?

Recommended Prophylactic Antibiotic Regimen for Cesarean Section

The correct answer is none of the options listed—the recommended regimen is cefazolin (a first-generation cephalosporin) 2g IV as a single dose within 60 minutes before skin incision, with the addition of azithromycin for women in labor or with ruptured membranes. 1, 2

Why the Listed Options Are Incorrect

Option A: Gentamicin + Ceftriaxone

• This combination is not the standard prophylactic regimen for cesarean section 2
• Gentamicin is reserved as an alternative component (with clindamycin) only for patients with documented penicillin/cephalosporin allergies 2
• Ceftriaxone plus metronidazole is used for suspected chorioamnionitis, not routine prophylaxis 2

Option B: Metronidazole Alone

• Metronidazole monotherapy is inadequate for cesarean prophylaxis 2
• While metronidazole provides anaerobic coverage, it lacks the gram-positive coverage essential for surgical site infection prevention 3
• Studies show metronidazole should be added to cefazolin, not used alone 3

Option C: No Antibiotics Needed

• This is incorrect and dangerous 1, 2
• Prophylactic antibiotics reduce postoperative infectious morbidity significantly 4, 5
• Without prophylaxis, endometritis rates can reach 16.4% compared to 1.3% with appropriate prophylaxis 5

Option D: Amoxicillin Only

• Amoxicillin is not the recommended first-line agent 1, 2
• First-generation cephalosporins (cefazolin) are superior and specifically recommended 1, 2

The Evidence-Based Correct Regimen

Standard Prophylaxis (All Women)

• Cefazolin 2g IV single dose administered 30-60 minutes before skin incision 1, 2
• This represents high-quality evidence with strong recommendation grade from ACOG 1, 2

Enhanced Prophylaxis (Women in Labor or with Ruptured Membranes)

• Add azithromycin to cefazolin for additional reduction in postoperative infections 1, 2
• This combination reduced endometritis from 16.4% to 1.3% in a large cohort study 5
• The dual regimen is supported by high-quality evidence with strong recommendation grade 2

For Penicillin/Cephalosporin Allergies

• Clindamycin 900mg IV plus gentamicin 5mg/kg/day as a single dose 2
• Administer clindamycin as a slow infusion to avoid infusion-related reactions 2

Critical Timing and Dosing Details

Timing

• Antibiotics must be given 30-60 minutes before skin incision, not after cord clamping 1, 2
• This pre-incision timing is crucial for optimal tissue levels during surgery 1

Single vs. Multiple Doses

• Single-dose prophylaxis is as effective as multiple doses 4, 6, 7
• No additional doses are needed if procedure duration is less than 4 hours 2
• If surgery exceeds 4 hours, consider one additional 1g cefazolin dose 2

Common Pitfalls to Avoid

• Do not delay antibiotics until after cord clamping—this outdated practice significantly reduces efficacy 1, 2, 5
• Do not use broad-spectrum agents routinely—first-generation cephalosporins are equally effective as second or third-generation agents for prophylaxis 4
• Do not prescribe extended courses—single-dose regimens have comparable efficacy with lower cost and reduced antibiotic resistance risk 6, 7
• Do not forget azithromycin in high-risk patients—women in labor or with ruptured membranes benefit significantly from dual therapy 1, 2, 5