A comparison of 3 antibiotic regimens for prevention of postcesarean endometritis: an historical cohort study

Background Prophylactic antibiotics are of proven value in decreasing the frequency of postcesarean endometritis. The beneficial effect of prophylaxis is enhanced when the antibiotics are administered before the surgical incision as opposed to after the clamping of the umbilical cord. However, the optimal antibiotic regimen for prophylaxis has not been established firmly. Objective The purpose of this study was to compare 3 different antibiotic regimens for the prevention of postcesarean endometritis. Study Design This retrospective historical cohort study was conducted at the University of Florida, which is a tertiary care facility that serves a predominantly indigent patient population. In the period January 2003 to December 2007, our standard prophylactic antibiotic regimen for all women who had cesarean delivery was cefazolin (1 g) administered immediately after the baby’s umbilical cord was clamped. In November 2008, we began to administer the combined regimen of cefazolin (1 g intravenously) plus azithromycin (500 mg intravenously); both were given 30-60 minutes before the skin incision. In the period of January-December 2014, we continued the dual agent regimen but based the dose of cefazolin on the patient’s body mass index: 2 g intravenously if the body mass index was 30 kg/m2 . The surgical technique was consistent throughout all 3 time periods. Our primary endpoint was the frequency of endometritis in each time period. This diagnosis was based on fever ≥37.5°C, lower abdominal pain and tenderness, the exclusion of other localizing signs of infection, and the requirement for administration of therapeutic antibiotics. In the first year after beginning the new antibiotic regimen, we also monitored the frequency of neonatal sepsis evaluations and compared it with the frequency that was recorded during the year immediately preceding the change in antibiotic regimens. Results During the entire period 2003-2014, 29,633 women delivered at our institution; 6455 women (22%) had a cesarean delivery. In the period January 2003 to December 2007, 1034 women had a primary or repeat cesarean delivery. One hundred seventy women (16.4%; 95% confidence interval, 14.4–18.4%) developed endometritis. In the period November 2008 to December 2013, 4484 women had a primary or repeat cesarean delivery. Fifty-nine patients (1.3%; 95% confidence interval, 1.0–1.7%) developed endometritis ( P < .0001 compared with period 1). In