Principal endpoints were the occurrence of postoperative endometritis and wound infection. Secondary endpoints were less common infection-related complications such as maternal sepsis, fascial dehiscence or evisceration, necrotizing fasciitis, pelvic abscess, and septic pelvic vein thrombophlebitis.
Of the women who were given prophylactic antibiotics, 88% received only a cephalosporin, 7% received only a broad-spectrum penicillin, and 6% received other regimens. Approximately 1% of patients received more than one antibiotic for prophylaxis.
Averting infection pays dividends
More than 90% of patients who have endometritis respond promptly to broad-spectrum antibiotic therapy. However, some women with postcesarean endometritis develop serious complications such as septic shock, septic pelvic vein thrombophlebitis, and pelvic abscess.
Treatment of wound infection is not so straightforward as treatment of endometritis. Wound infections may well require surgical intervention to drain an incisional abscess. They also necessitate a change in antibiotic therapy, and they are one of the two most important risk factors for fascial dehiscence and intestinal evisceration.
Multiple studies have confirmed that antibiotic prophylaxis significantly reduces the risk of endometritis and wound infection in women who undergo cesarean after the start of labor, with or without ruptured membranes.7,8 Recent publications have also demonstrated that prophylaxis before the start of surgery offers a greater protective effect than administration after the infant’s umbilical cord is clamped.9,10 Other investigations have demonstrated that broader-spectrum prophylaxis further improves outcomes in women undergoing cesarean delivery.11,12
WHAT THIS EVIDENCE MEANS FOR PRACTICE
Antibiotic prophylaxis reduces the frequency of postcesarean endometritis and wound infection, even in very low-risk patients. I strongly support the use of prophylactic antibiotics in all women undergoing cesarean delivery. I believe that the best available evidence supports the use of cefazolin (1 g) plus azithromycin (500 mg), administered intravenously before the start of surgery.9-12
Administer antibiotics before making the incision for greatest effectiveness
Owens SM, Brozanski BS, Meyn LA, Wisenfeld HC. Antimicrobial prophylaxis for cesarean delivery before skin incision. Obstet Gynecol. 2009;114(3):573–579.
In this retrospective investigation, Owens and colleagues compared antibiotic prophylaxis in two groups of women undergoing cesarean delivery:
- 4,229 women who received antibiotics after the infant’s umbilical cord was clamped, from July 2002 to November 2004 (Group 1)
- 4,781 women who received antibiotics before the skin was incised, from June 2005 to August 2007 (Group 2).
Both scheduled and unscheduled cesarean deliveries were included, as were women who received antibiotics intrapartum for group B streptococcus prophylaxis and treatment of chorioamnionitis. The most commonly used antibiotic was intravenous cefazolin (1 g).
After excluding women who received group B streptococcus prophylaxis or intrapartum treatment of chorioamnionitis, the authors demonstrated a nearly 50% reduction in the rate of endometritis among women who received antibiotics before surgery (OR, 0.54; 95% CI, 0.38–0.75). They also documented a 30% reduction in the rate of wound infection in these patients (OR, 0.72; 95% CI, 0.55–0.46).
Details of the trial
Principal outcome measures were the rates of maternal endometritis and wound infection and rates of proven and presumed neonatal infection. The mean age and racial distribution were similar in the two groups, but the percentage of patients treated on a resident teaching service was lower in Group 2 (14.9% vs. 18.9%; P < .001). The two groups did not differ in mean body mass index or in the percentage of patients who were in labor before surgery. Colonization with group B streptococcus was more common in Group 2 (24.4% vs. 22.2%; P = .5). However, chorioamnionitis was less prevalent in Group 2 (5.6% vs. 10.3%; P < .001).
The rates of culture-proven neonatal infection within the first 3 days of life (early-onset infection) were similar between groups (1.3% in Group 1 vs. 0.7% in Group 2). Culture-proven late-onset neonatal infection was less common in Group 2 (1.8% vs. 5.7%; P < .001). The groups did not differ in the proportion of newborns treated for presumed infection (24.1% in Group 1 vs. 22.2% in Group 2).
Plentiful data confirm the superiority of preoperative administration
Endometritis is the most common postoperative complication associated with cesarean delivery. Wound infection is less common but more likely to lead to prolonged postoperative morbidity and extended hospitalization. Reducing both of these complications is a critical clinical objective.
Virtually without exception, every investigation has confirmed that prophylactic antibiotics reduce the frequency of postcesarean endometritis and, usually, wound infection as well. One dose of a given antibiotic is clearly as effective as multiple doses.
Classic animal investigations by Burke demonstrated that prophylaxis was most effective when antibiotics were present in tissue prior to the surgical incision.13 Nevertheless, early investigators in obstetrics argued that preoperative exposure to antibiotics increased the likelihood that the neonate would require an evaluation for sepsis and that delaying antibiotics until after cord clamping did not compromise the effectiveness of prophylaxis.14,15