Fetal heart rate patterns complicated by chorioamnionitis and subsequent cerebral palsy in Japan

Aim This retrospective study was performed to investigate whether certain fetal heart rate patterns were associated with subsequent cerebral palsy (CP) in infants with chorioamnionitis at or near term. Methods We used cases registered by the Japan Obstetric Compensation System for CP, which is a nationwide population‐based database. Among them, 133 infants with chorioamnionitis who were born at ≥34 weeks of gestation were enrolled. All infants underwent magnetic resonance imaging (MRI), and all fetal heart rate charts had been interpreted according to the National Institute of Child Health and Human Development criteria, focusing on antepartum and immediately before delivery. Results The incidence of CP after chorioamnionitis at ≥34 weeks of gestation was 0.3 per 10 000 in Japan. Between the clinical (24%) and subclinical groups (76%), the incidence of abnormal fetal heart rate patterns did not differ. According to the MRI classification, 88% of the infants with CP showed hypoxic–ischemic encephalopathy. Half of the infants with CP experienced terminal bradycardia, leading to severe acidosis and exclusively to hypoxic–ischemic encephalopathy. In another half, who did not experience bradycardia, 80% had moderate acidosis (pH 7.00–7.20) resulting in hypoxic–ischemic encephalopathy, and the remaining 20% showed non‐acidosis resulting in brain damage other than hypoxic–ischemic encephalopathy. The fetal heart rate patterns before the terminal bradycardia showed that the incidence rates of late deceleration or decreased variability were high (>60%). Conclusion Fifty percent of pregnant women with chorioamnionitis‐related CP had terminal bradycardia that exclusively resulted in hypoxic–ischemic encephalopathy.