(1164) Maternal outcomes of first- versus second-line intrapartum antibiotic prophylaxis for group B streptococcus: a retrospective-study

Objective:
The incidence of maternal infectious morbidity according to the intrapartum antibiotic prophylaxis (IAP) regimen used for Group B streptococcus (GBS) prophylaxis is poorly described. We aimed to compare maternal peripartum infections and microbiological outcomes among GBS carriers according to IAP regimen.

Study Design:
This retrospective study included women hospitalized in a tertiary university-affiliated hospital between March 2021 and March 2024, who were GBS positive at term and received first-line ampicillin (n=1833), or second-line clindamycin (n=78) due to penicillin allergy. The co-primary outcomes were clinical chorioamnionitis and neonatal intensive care admission rates. Univariate and multivariate analyses were performed. Chorioamniotic swabs were obtained after delivery, and microbiological outcomes were compared according to IAP regimen.

Results: Among GBS carriers who received clindamycin vs. ampicillin, the rates were higher of chorioamnionitis (p< 0.001), intrapartum fever (p< 0.001), postpartum fever (p=0.001) and antibiotics use (p< 0.001) (Figure). The cesarean delivery rates were similar (p=0.086). The rate of neonatal intensive care admission and other neonatal complications were similar. In multivariate analysis, the factors that were independently associated with clinical chorioamnionitis were: clindamycin-IAP, odds ratio (OR) 20.1, 95% confidence interval (CI) (6.6-61.4), p< 0.001; cervical ripening by catheter balloon, OR 4.1, 95%CI (1.2-13.6), p=0.023; and prolonged rupture of membranes, OR 4.9, 95%CI (1.6-15.7), p=0.006 (Table). In chorioamniotic swabs, among women who received clindamycin vs. ampicillin, rates were higher of positive GBS isolates, 28% vs. 11%, p< 0.001 and of overall positive cultures, 32.1% vs. 16.4%, p< 0.001.

Conclusion: Clindamycin compared with ampicillin was associated with a higher rate of maternal peripartum infectious morbidity.

This underscores the importance of minimizing clindamycin use for GBS prophylaxis. Further research is warranted to evaluate alternative second-line IAP options and their effectiveness in preventing GBS-related infections.