ACOG Practice Bulletin No. 120: Use of prophylactic antibiotics in labor and delivery.

Effective prophylactic antibiotic agents are active against most but not all potential pathogens, which usually are endogenous flora. The goal of antibiotic prophylaxis is to prevent infection, not to cure or treat disease. In contrast to the therapeutic use of antibiotics, prophylaxis must be administered before the potential exposure, and usually for a short duration (less than 24 hours). The goal of prophylactic antibiotic use is to have therapeutic tissue levels in place at the time microbial contamination might occur. Delaying administration by even a few hours reduces or eliminates the benefit of prophylaxis. Ideally, the agent of choice should be long acting, narrowly focused on the likely bacteria, inexpensive, and have a low incidence of adverse effects. Resistance Risks of Prophylactic Antibiotics Although the risks of inappropriate antibiotic use may be difficult to recognize in any individual patient, the broader effect of the increasing use of antibiotics can be seen in the hospital setting. Antimicrobial prophylaxis has been shown to result in marked changes in an individual’s skin flora, with increases in resistant flora seen postoperatively (1). This appears to be the result of selection of resistant endogenous flora by prophylactic antibiotics, as well as the nosocomial acquisition of resistant micro-organisms. In labor and delivery, awareness of the potential adverse effects of resistant bacterial infections on neonates has been increasing. A comparison of very low birth weight neonates (less than 1,500 g) born between Use of Prophylactic Antibiotics in Labor and Delivery