Intrapartum fetal heart rate patterns and perinatal outcome in chorioamnionitis at or beyond 34 weeks of gestation

Aim: To investigate intrapartum fetal heart rate (FHR) patterns in women with chorioamnionitis at or beyond 34 weeks of gestation in relation to neonatal outcome and to compare clinical and subclinical chorioamnionitis.

Methods: A retrospective questionnaire survey on deliveries during 2015 was conducted by the Perinatology Committee of the Japan Society of Obstetrics and Gynecology from 2016 to 2018. A total of 498 singleton births complicated by chorioamnionitis delivered at ≥34 weeks of gestation without major congenital malformations were included. The subjects were divided into clinical and subclinical chorioamnionitis groups based on Lencki's criteria. Poor perinatal outcome was defined as death or brain damage. We analyzed clinical features, FHR patterns in the last 2 h before delivery, gestational age, birthweight, Apgar score, umbilical arterial blood gas analysis, and infant's outcome.

Results: Incidence of chorioamnionitis at ≥34 weeks of gestation was 0.59% (522/87827). Clinical and subclinical chorioamnionitis comprised 240 and 258 cases, respectively. Abnormal FHR patterns (late deceleration or decreased baseline variability) were significantly associated with poor perinatal outcome. Combined late deceleration and decreased variability showed low positive predictive value (12.8%) and high negative predictive value (99.5%), and was significantly associated with long-term poor outcome in clinical chorioamnionitis only (odds ratio: 29.4, p < 0.01). Poor perinatal outcome showed no significant difference between the clinical and subclinical chorioamnionitis groups.

Conclusions: Combined late deceleration and decreased variability could predict poor perinatal outcome in clinical chorioamnionitis. Poor perinatal outcome occurred in infants born to mothers with clinical and subclinical chorioamnionitis.