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Women scheduled for cesarean section should be started on antibiotics an hour before delivery, according to new recommendations from the American College of Obstetricians and Gynecologists (ACOG).

The only exceptions would be patients already on appropriate antibiotics -- to combat chorioamnionitis, for instance -- and emergency cases, which should get antibiotics as soon as possible, according to an ACOG committee opinion statement.

Although antimicrobial prophylaxis to reduce postoperative maternal infections is already common practice for C-sections, clinicians need to stop waiting until after clamping the umbilical cord to administer them, according to the statement.

Preoperative administration is more effective, the writing committee explained in the September issue of Obstetrics & Gynecology.

Compared with administration of antibiotics after umbilical cord clamping, the statement cited studies showing:

• Fewer wound infections (0.6% when given two hours before skin incision versus 1.4% within three hours after incision)
• Significantly lower endometriosis rates (1% when given 15 to 60 minutes before C-section versus 5% after clamping in one trial and 7.8% when given at incision versus 14.8% after clamping in another)
• Significantly lower total postoperative infection rates (4.5% when given 15 to 60 minutes before C-section versus 11.5% after clamping)

Although an additional small randomized trial showed no significant maternal benefit from preoperative antibiotics, it showed no harm.

Concerns that exposure could have a negative impact on the baby by masking positive bacterial culture results or leading to antibiotic resistant infections are unfounded, the committee concluded.

Randomized trials have shown no difference in rates of neonatal sepsis overall or from resistant organisms or in rate of admission to a neonatal intensive care unit, although all were underpowered to analyze these secondary outcome measures.

The recommendation for starting prophylaxis within 60 minutes of the start of cesarean delivery should allow a sufficient serum level to be established by the time of skin incision, the statement noted.

Therapeutic levels need to be maintained throughout the operation, so the same dose should be readministered at intervals one or two times the drug's half-life, according to the new recommendation.

First-generation cephalosporins and other narrow-spectrum antibiotics effective against gram-positive and gram-negative bacteria as well as against some anaerobic bacteria are the typical prophylactic choice in the cesarean setting.

Clindamycin (Cleocin) with gentamicin (Garamycin) would be a reasonable alternative for women with a significant allergy to beta-lactam antibiotics, according to the ACOG statement.

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