LAUSR

BACKGROUND A recent large clinical trial demonstrated an almost 50% decrease in postoperative infection in women who were laboring and/or had ruptured membranes for greater than four hours who received azithromycin in addition to standard preoperative antibiotic prophylaxis at the time of cesarean. Given these results, our institution made a policy change in May 2017 to add azithromycin to standard preoperative prophylaxis for all cesarean deliveries. OBJECTIVE Valuate the clinical effectiveness of adding azithromycin to cesarean preoperative antibiotic prophylaxis. STUDY DESIGN We conducted a before-and-after cohort study of women delivered via cesarean at our institution. The pre-implementation group included women who delivered 3/1/16-2/28/17 (prior to institutional practice change adding azithromycin to standard preoperative prophylaxis), and the post-implementation group included women who delivered 9/1/17-8/31/18 (allowing a 6-month period for uptake of the practice change). The primary outcome was a composite of postoperative infections (endometritis, wound infection, other maternal infections). Unadjusted and adjusted risk ratios (RR) and 95% confidence intervals were estimated using a modified Poisson regression model. RESULTS In the pre-implementation (n=1171) and post-implementation (n=1168) groups, the incidence of the composite outcome was 4.7% and 5.3%, respectively (p=0.49). Both unadjusted (RR 1.13 [95% CI 0.78, 1.62]) and adjusted (a; aRR 1.06 [0.74, 1.52]) comparisons were not significantly different. Results also were statistically non-significant, but in the direction of lower rates of infection, in the after cohort for women in labor and/or with ruptured membranes for 4 or more hours (RR 0.88 [0.56, 1.39]; aRR 0.82 [0.52, 1.30]) and for women with clinical chorioamnionitis (RR 0.37 [0.08, 1.67]; data too sparse for adjusted analysis). In the subgroup of women who were not in labor, the after cohort had a statistically non-significant increased risk of the composite outcome in both unadjusted (RR 1.53 [0.86, 2.72]) and adjusted comparisons (aRR 1.48 [0.83, 2.65]). CONCLUSIONS In clinical practice, the addition of azithromycin to standard cesarean preoperative antibiotic prophylaxis may have an effect size smaller than seen in the large clinical trial prompting this practice change. Extrapolation of use to non-laboring women may be ineffective altogether.