Preoperative cefazolin rather than clindamycin or metronidazole is associated with lower postpartum infection among women with chorioamnionitis delivering by cesarean delivery

BACKGROUND: The optimal antibiotic regimen to prevent maternal postpartum infection among high-risk women treated for chorioamnionitis delivering by cesarean delivery remains to be defined. Emerging data suggest that cefazolin decreases the risk of cesarean surgical site infection. OBJECTIVE: To investigate whether intrapartum antibiotic therapy with cefazolin versus the current standard clindamycin or metronidazole decreases the risk of postpartum infectious morbidity among women delivering by cesarean delivery who were receiving a base regimen of ampicillin or penicillin with gentamicin for chorioamnionitis. MATERIALS AND METHODS: A secondary analysis from the Maternal-Fetal Medicine Units Network (MFMU) Cesarean Registry. We included women who delivered by cesarean delivery with presumptive chorioamnionitis (intrapartum fever >100.4 degrees F and receipt of intrapartum antibiotics). All women received a base regimen of penicillin or ampicillin with gentamicin. We compared antibiotic therapy with cefazolin versus clindamycin or metronidazole. The primary outcome was a composite of postpartum maternal infection, including endometritis and surgical site infection. Multivariable logistic regression was used, adjusting for age, parity, race/ethnicity, insurance, body mass index at delivery, tobacco use, pregestational diabetes, American Society of Anesthesiologists classification, trial of labor prior to cesarean delivery, and postpartum antibiotics. RESULTS: Among 1105 women with presumptive chorioamnionitis who delivered by cesarean delivery, 22.0% (n = 244) received cefazolin and 77.9% (n = 861) received clindamycin or metronidazole. Most women were in labor prior to cesarean delivery (93.8%) and received postpartum antibiotics (88.4%). Almost one-tenth (9.5%) were diagnosed with a postpartum infection, most commonly endometritis (80.9%), followed by surgical site infection (20.9%) (not mutually exclusive). Women treated with cefazolin rather than clindamycin or metronidazole had lower odds of postpartum infectious morbidity (adjusted odds ratio, 0.49; 95% confidence interval, 0.26-0.90). This association held when the outcome was restricted to surgical site infection (adjusted odds ratio, 0.11; 95% confidence interval, 0.01-0.92) but not endometritis. Similar results were observed with propensity score analysis. CONCLUSION: Among women delivering by cesarean delivery who were treated for chorioamnionitis, additional antibiotic therapy with cefazolin decreased the risk of postpartum infection, primarily surgical site infection, compared to the current standard clindamycin or metronidazole.