Maternal morbidity following cesarean delivery is estimated to be eight times greater than that following vaginal delivery and may add more than $10 billion annually to U.S. health care costs. Infection at the surgical site appears to be a significant source of morbidity, even though the reported infection rate varies substantially across studies, and the reasons for this wide variation are poorly understood. Tran and colleagues conducted a prospective study to identify postoperative complications and risk factors for surgical site infections following cesarean delivery.
A cohort of more than 900 women who delivered by cesarean section at a large Vietnamese hospital was studied over a four-month period in 1997. Data were collected on the preoperative status of the mother, including age, parity, body mass index and significant comorbidities. Pregnancy data were collected as well, such as gestation, status of membranes and history of obstetric complications and attempted induction of labor. Data also were collected on the surgical and anesthesia techniques used and postoperative complications. Patients were monitored for signs of infection for 30 days postoperatively. If fever developed, a leukocyte count was obtained. If infection was suspected, additional tests such as urine and wound cultures were performed. All surgical wounds were regularly inspected by the researchers, and all patients received parenteral antibiotics preoperatively. Surgical complications included intraoperative bleeding that required transfusion, postoperative bleeding and injury to adjacent organs.
Of the 969 women enrolled in the study, 157 (16.2 percent) had febrile complications, and 95 (9.8 percent) had surgical site infections. Other sites of infection were the urinary tract, chest and gastrointestinal tract. The initial univariate analysis identified 10 factors related to surgical site infections, but multiple regression analysis identified only seven as predictive of postoperative surgical site infection. For a complete list of independent risk factors for infection as identified by multiple regression analysis, see the accompanying table. Preoperative uterine infection or infection at a remote site was the most significant risk factor, followed by anesthesia risk score and body mass index. The most significant surgical variable was blood loss, with a 30 percent increase in risk of infection for each additional 100 mL of blood lost during surgery. Duration of surgery also appeared to increase the risk of infection, but the number of prolonged cases was not sufficient to assess the predictive value of this variable.
|Variables||Coefficient||Odds ratio||95% confidence interval||P|
|Preoperative remote infection||2.8||16.5||2.1, 128.3||.007|
|American Society of Anesthesiologists score ≥3||1.7||5.3||1.1, 24.0||.029|
|Body mass index (every five-unit increment)||0.7||2.0||1.3, 3.0||.001|
|Blood loss (every 100-mL increment)||0.2||1.3||1.1, 1.5||.005|
The authors conclude that risk factors for surgical site infection following cesarean delivery are infection before surgery, obesity, nulliparity, preeclampsia and poor general health.