What is the primary indication for prophylactic antibiotics in a postpartum patient with a 5-hour rupture of membranes, 4 cm cervical dilation, manual placenta removal, and a 2-degree perineal tear, who is stable and afebrile?

Manual Placenta Removal is the Primary Indication for Prophylactic Antibiotics

The correct answer is C: Manual placenta removal is the primary indication for prophylactic antibiotics in this clinical scenario. Manual removal of the placenta significantly increases the risk of postpartum endometritis by introducing bacteria into the uterus, and antibiotic prophylaxis has been shown to reduce infectious morbidity 1.

Why Manual Placenta Removal Requires Antibiotics

Manual placenta removal introduces vaginal and perineal bacteria into the uterine cavity, substantially increasing endometritis risk. The evidence demonstrates:

• Manual placental extraction increases postcesarean infection rates from 15% to 27% compared to spontaneous delivery (relative risk 0.6,95% CI 0.4-0.9, p=0.01), even when prophylactic antibiotics are given 2
• When combined with ruptured membranes, manual removal increases infection rates from 20% to 38% (relative risk 0.5,95% CI 0.3-0.9, p=0.02) 2
• The recommended regimen is a single dose of ampicillin 2g IV (or cefazolin 1g IV) plus metronidazole 500mg IV 1

Why the Other Options Are Incorrect

A. Rupture of Membranes for 5 Hours (Not >6 Hours)

• This patient's membranes were ruptured for only 5 hours, which does not meet the threshold for routine antibiotic prophylaxis 3, 4
• Prophylactic antibiotics are recommended after 18 hours of membrane rupture according to CDC guidelines, not 6 hours 3, 4
• At term with intact labor progression and only 5 hours of ROM, this alone would not mandate antibiotics 3

B. Second-Degree Perineal Tear

• Second-degree tears do not require routine antibiotic prophylaxis 5
• Only third- and fourth-degree perineal lacerations (obstetrical anal sphincter injuries, OASIS) have evidence supporting prophylactic antibiotics 6
• A prospective randomized controlled study showed antibiotics reduced wound complications in OASIS repairs (purulent discharge 17.2% vs 4.1%, p=0.04), but this evidence applies specifically to severe perineal trauma, not second-degree tears 6

Recommended Antibiotic Regimen

For manual placenta removal after vaginal delivery:

• Ampicillin 2g IV plus metronidazole 500mg IV (single dose) 1
• Alternative: Cefazolin 1g IV plus metronidazole 500mg IV if penicillin allergy 1
• If the patient already received GBS prophylaxis (ampicillin or penicillin), give only metronidazole 500mg IV 1

Critical Clinical Pitfalls to Avoid

• Do not withhold antibiotics after manual placenta removal simply because the patient appears stable and afebrile - infection can develop later, and prophylaxis is most effective when given at the time of the procedure 1
• Do not confuse the timing thresholds: ROM >18 hours (not 6 hours) is the indication for antibiotics based on membrane rupture alone 3, 4
• Do not give antibiotics for second-degree tears - this wastes resources and contributes to antibiotic resistance without evidence of benefit 5
• Ensure anaerobic coverage with metronidazole - the uterine cavity contains both aerobic and anaerobic bacteria, and metronidazole is essential for comprehensive coverage 1