Intrauterine Contraction Monitoring in Chorioamnionitis: A Secondary, Blinded Analysis of a Randomised Controlled Trial Cohort

Objective: To study the effects of chorioamnionitis on uterine activity and to investigate associations between external and intrauterine monitoring methods and neonatal outcomes. Design: Secondary analysis of a randomised controlled trial cohort. Setting: Two labour wards, in a university tertiary hospital and a central hospital. Population: Parturients with singleton pregnancies, gestational age ≥ 37 weeks and fetus in cephalic position. Clinical chorioamnionitis developed in 8.6% of cases (n = 130/1504). Methods: Analyses of uterine activity (contractions/10 min or intrauterine pressure in Montevideo units) during the 4 h before birth adjusted for maternal characteristics and intrapartum factors. Main Outcome Measures: Uterine activity with or without chorioamnionitis and the intervention of external versus intrauterine monitoring in relation to fetal distress (admission to neonatal intensive care with umbilical artery pH ≤ 7.10 or 5-min Apgar score < 7), stratified by chorioamnionitis status. Results: Uterine contraction frequency/10 min decreased in labours with chorioamnionitis during the final hour preceding birth (4.2 [SD 1.1] vs. 3.9 [SD 1.2], adjusted regression coefficient −0.383, 95% CI −0.654 to −0.112, p = 0.006) compared to non-infected labors. In chorioamnionitis cases, mean frequency/10 min during last 4 h was higher with external versus intrauterine monitoring (4.2 [SD 0.8] vs. 3.8 [SD 0.9], MD 0.39, 95% CI 0.02–0.76, p = 0.038), and the intrauterine monitoring group had a lower incidence of fetal distress (6.7% vs. 23.1%, OR 0.24, 95% CI 0.07–0.79, p = 0.013). Conclusions: Chorioamnionitis impairs uterine activity. Intrauterine monitoring may provide more accurate contraction analysis than external tocodynamometry and help reduce fetal compromise during labours complicated by chorioamnionitis.