When should a dose of antibiotic be administered preoperatively to a 35-week gestation pregnant woman with premature premature rupture of membranes (PPROM) and intrauterine growth restriction (IUGR) undergoing a cesarean section (CS)?

Antibiotic Administration for Pregnant Woman with PPROM Undergoing Cesarean Section

Administer antibiotics immediately upon admission for this 35-week pregnant woman with PPROM, not waiting until the preoperative period, as she requires both latency antibiotics for PPROM management and GBS prophylaxis given her preterm gestational age and ruptured membranes. 1, 2

Immediate Antibiotic Management at Admission

Since this patient has PPROM at 35 weeks gestation, she meets criteria for immediate antibiotic therapy regardless of cesarean section timing:

• Start IV ampicillin 2g every 6 hours plus erythromycin 250mg IV every 6 hours immediately upon admission 2, 3
• This regimen serves dual purposes: latency antibiotics for PPROM and adequate GBS prophylaxis, as the CDC confirms that ampicillin 2g IV followed by 1g IV every 6 hours for at least 48 hours provides sufficient GBS coverage 2
• At 35 weeks with ruptured membranes, she has multiple indications for GBS prophylaxis even with unknown GBS status: delivery <37 weeks gestation and membrane rupture 1

Critical Timing Considerations

The antibiotics should have been started at hospital admission when PPROM was diagnosed, not delayed until the decision for cesarean section was made:

• Women with rupture of membranes at <37 weeks gestation should receive antibiotics at hospital admission 1
• The standard 7-day PPROM antibiotic course consists of 48 hours IV therapy followed by 5 days oral therapy, but if cesarean delivery occurs during the initial IV phase, continue the IV antibiotics until delivery 2, 3
• If she has already been receiving the ampicillin/erythromycin regimen for PPROM, simply continue it through delivery—no additional GBS prophylaxis is needed 2

Preoperative Surgical Prophylaxis

For the cesarean section itself, administer cefazolin 2g IV 30-60 minutes before skin incision as standard surgical prophylaxis:

• This timing (30-60 minutes pre-incision) ensures therapeutic tissue concentrations at the time of surgical incision 4, 5, 6
• The cefazolin dose should be given even if she is already receiving ampicillin for PPROM/GBS prophylaxis, as surgical prophylaxis addresses different organisms and infection risks 1, 6
• Consider adding azithromycin 500mg IV to cefazolin for cesarean delivery in the setting of ruptured membranes for additional reduction in postoperative infections 4

Algorithm for This Clinical Scenario

If antibiotics were NOT started at admission (common pitfall):

1. Immediately start IV ampicillin 2g, then 1g every 6 hours plus erythromycin 250mg IV every 6 hours 2, 3
2. Continue this regimen until delivery
3. Add cefazolin 2g IV 30-60 minutes before cesarean incision 4, 5, 6
4. Consider adding azithromycin 500mg IV with the cefazolin 4

If antibiotics WERE appropriately started at admission:

1. Continue the existing ampicillin/erythromycin regimen through delivery 2
2. Add cefazolin 2g IV 30-60 minutes before cesarean incision 4, 5, 6
3. Consider adding azithromycin 500mg IV with the cefazolin 4

Common Pitfalls to Avoid

• Waiting until the operating room to start antibiotics in a PPROM patient—this delays both latency antibiotics and GBS prophylaxis that should have been initiated at admission 1, 2
• Assuming surgical prophylaxis alone is adequate—PPROM at <37 weeks requires specific antibiotic management beyond standard cesarean prophylaxis 1, 2
• Using amoxicillin-clavulanate (Augmentin)—this combination increases risk of neonatal necrotizing enterocolitis and should be avoided; amoxicillin alone is safe 2, 3
• Giving only oral antibiotics for GBS prophylaxis—oral antibiotics are inadequate for GBS prophylaxis 2, 4
• Discontinuing PPROM antibiotics if GBS screen returns negative—while GBS prophylaxis can be stopped if the screen is negative, the latency antibiotics for PPROM should continue as planned at this preterm gestational age 2

Special Considerations for This Patient

• If GBS status becomes available and is positive, continue ampicillin through delivery 2
• If GBS status is negative, GBS prophylaxis can be discontinued but continue erythromycin as part of PPROM management 2
• The IUGR diagnosis does not change antibiotic management but reinforces the importance of prompt delivery and infection prevention 1
• If signs of chorioamnionitis develop, switch to broad-spectrum antibiotics (clindamycin plus gentamicin) that include GBS coverage 1, 4