Controversies in OB/GYN: Should patients undergoing low-risk C/S receive antibiotic prophylaxis?

August 1, 2006

Dr. Chelmow maintains that the benefits and cost savings of prophylactic antibiotics are clear. Drs. Marder and Boggess, on the other hand, say the drugs should only be used when infection risk factors justify it.

Yes. The benefits-and cost savings-are clear.

C/S done on a woman who has intact membranes and is not in labor carries a lower risk for infectious complications than procedures done during labor or with ruptured membranes. Nonetheless, infectious morbidity-and particularly fever and endometritis-do occur. Our meta-analyses of nine prior studies of antibiotic prophylaxis in this setting showed that without pretreatment, patients had a 24% risk of fever, 11% risk of endometritis, and up to a 10% risk of wound infection.3,4 Antibiotic prophylaxis is routinely recommended for C/S with labor or ruptured membranes, yet its routine administration for low-risk C/S is controversial despite a significant risk of infection.

The most recent Practice Bulletin from the American College of Obstetricians and Gynecologists notes that the benefit of antibiotic prophylaxis in these patients is "less clear."5 I would argue, however, that it actually is quite clear. We have excellent data showing that antibiotic prophylaxis for patients undergoing low-risk C/S decreases infectious deaths. Clear efficacy was noted in an update of our original meta-analysis, which included two individual trials in this area.4 Combining results of the smaller trials produced a statistically significant and clinically important decrease in endometritis (RR of 0.18, 95% CI [0.07, 0.45]) and fever (RR of 0.47, 95% CI [0.32, 0.68]). We did not, however, find evidence of reduction in wound infections.

I believe that earlier studies failed to show a benefit for antibiotic prophylaxis because the patients had such low baseline risks that a much larger sample size was needed to reach statistical significance. Most of the individual studies are underpowered to show even moderate risk reductions from the low baseline risks. Meta-analysis of the body of work showed that the individual trends in risk reduction, when combined, were highly significant. The risk reductions occurred across all studies, regardless of the antibiotic used and in a variety of different populations, suggesting consistent effect.

Preventing infectious complications of C/S is important. Even in a low-risk population, endometritis can extend hospital stays, increase treatment cost, and heighten pain, and in rare instances, it can lead to a need for further surgery or placement of a drain. Fever is less of a concern, but the risk seems to be reduced significantly by antibiotic prophylaxis even though we do not know the mechanism of prevention. Reducing the risk of fever is beneficial, because this complication is disturbing to a patient and costly to evaluate in terms of dollars and staff time.

Issues beyond efficacy

Providing routine antibiotic prophylaxis raises two potentially significant issues: cost and antibiotic resistance.