The American College of Obstetricians and Gynecologists (ACOG) has released a practice bulletin about the use of prophylactic antibiotics during labor and delivery. The bulletin presents a review of clinical situations in which prophylactic antibiotics frequently are prescribed and weighs the evidence supporting the use of antibiotics in these situations. The full report appeared in the October 2003 issue of Obstetrics and Gynecology.

Development of Resistant Organisms

Antimicrobial prophylaxis has been shown to increase resistant skin flora postoperatively; studies have reported colonization rates of 66 to 91 percent. Awareness of the potential risks of resistant bacterial infections has been increasing. A comparison of very-low-birth-weight neonates (i.e., less than 1,500 g [3 lb, 5 oz]) born between 1998 and 2000 with those born between 1991 and 1993 showed a reduction in early-onset neonatal sepsis from group B streptococci and an increase in sepsis caused by Escherichia coli. Sepsis in very-low-birth-weight neonates with ampicillin-resistant E. coli is more likely to be fatal than infection with susceptible strains. According to ACOG, the increases in E. coli sepsis and the increasing resistance to ampicillin appear to be confined to preterm and low-birth-weight neonates. In addition to resistant E. coli, group B streptococci isolates resistant to erythromycin and clindamycin have been reported.

Clinical Considerations and Recommendations

Evidence is insufficient to recommend antibiotic prophylaxis for emergency or prophylactic cervical cerclage. Few studies have evaluated the use of antibiotics during prophylactic cervical cerclage. Because the rate of complications is low (i.e., 1 to 5 percent), a study with a sample size large enough to determine the benefits of prophylactic antibiotic therapy would be difficult to implement.

Antibiotic prophylaxis may be considered for patients with premature rupture of membranes, particularly in cases of extreme prematurity, to prolong the latency period between membrane rupture and delivery. Certain broad-spectrum antibiotics lead to improved latency and may be particularly useful in cases of extreme prematurity. However, prolonged latency does not necessarily result in improved neonatal outcomes. Therefore, emerging data about resistant bacteria make it necessary to assess the risks and benefits for each patient.

According to ACOG, all high-risk patients undergoing cesarean delivery should receive prophylaxis with narrow-spectrum antibiotics such as cephalosporin. Several well-designed studies have documented the efficacy of prophylactic antibiotics in reducing the rates of postpartum endometritis and wound infection in patients who have undergone a cesarean delivery and are at high risk for infection. High-risk patients include those who have had cesarean deliveries after membrane rupture or labor and patients who undergo emergency procedures for which preoperative cleansing may have been inadequate. Other patients who may be at increased risk for postoperative infection include patients whose surgeries last for more than one hour and those who experience high blood loss. Risks of febrile morbidity, urinary tract infection, and wound infection also are reduced by antibiotic prophylaxis.

Whether patients at lower risk for infection benefit from antibiotic therapy is less clear. No differences in rates of wound infection, endometritis, urinary tract infection, pneumonia, or febrile morbidity were noted in a randomized controlled study of 480 women undergoing cesarean delivery. In a prospective study of 82 women, the incidence of febrile morbidity and endometritis was reduced by antibiotic prophylaxis. Although the evidence is inconclusive, prophylactic antibiotics are recommended in low-risk patients undergoing cesarean delivery.

In patients undergoing uncomplicated obstetric delivery who have certain cardiac conditions (i.e., prosthetic cardiac valves, previous bacterial endocarditis, complex cyanotic congenital cardiac malformations, surgically constructed systemic pulmonary shunts or conduits), prophylaxis for bacterial endocarditis is optional. However, antibiotics are recommended if the delivery is complicated by intra-amniotic infection. Prophylaxis ideally should be given shortly before delivery (within 30 minutes) and should not be given for more than six to eight hours.