Predictors of Severe Histological Chorioamnionitis and Associated Neonatal Outcomes in Term Intrapartum Clinical Chorioamnionitis: A Retrospective Cohort Study

Background and Objectives: Intrapartum clinical chorioamnionitis at term is a complication associated with adverse maternal and neonatal outcomes. We aimed to identify factors independently associated with severe histological chorioamnionitis in women with clinical chorioamnionitis at term and with severe histological chorioamnionitis accompanied by neonatal intensive care unit (NICU) admission, considered the most severe end of the spectrum. Materials and Methods: We retrospectively identified all women with a diagnosis of clinical chorioamnionitis during labor at term between 2017 and 2022. Maternal characteristics and maternal and neonatal outcomes were extracted from medical records. The study population was stratified by the presence or absence of histological chorioamnionitis. Results: Out of 12,332 women, 171 (1.4%) singleton pregnant women had an intrapartum diagnosis of clinical chorioamnionitis at term. A total of 96 (56.1%) were confirmed with severe histological chorioamnionitis. Thick meconium-stained amniotic fluid (MSAF) (OR = 5.88; 95% CI 1.12-30.86, p = 0.035) and advanced maternal age (OR = 1.14, 95% CI 1.01-1.29, p = 0.024) were independently associated with severe histologic chorioamnionitis. In women with severe acute histological chorioamnionitis, we observed a higher prevalence of neonatal NICU admission and longer NICU stay. Factors independently associated with severe histologic chorioamnionitis accompanied by adverse neonatal course (NICU admission) were maternal age, fetal tachycardia and thick meconium-stained amniotic fluid. Conclusions: The diagnosis of clinical chorioamnionitis has a low positive predictive value for intra-amniotic infection or inflammation. Factors such as maternal age, thick meconium-stained amniotic fluid and fetal tachycardia may help identify patients with underlying intra-amniotic infection and those at risk of worse perinatal outcomes. Improved identification may help avoid both over- and undertreatment and guide interventions aimed at preventing adverse neonatal outcomes.