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.