Histological Chorioamnionitis Is Increased at Extremes of Gestation in Stillbirth: A Population-Based Study

Objective . To determine the incidence of histological chorioamnionitis and a fetal response in stillbirths in New South Wales (NSW), and to examine any relationship of fetal response to spontaneous onset of labour and to unexplained antepartum death. Study Design . Population-based cohort study. Setting . New South Wales Australia. Population . All births between 2002 and 2004 with stillbirths reviewed and classified by the state perinatal mortality review committee. Methods . Record linkage of the Midwives Data Collection and the Perinatal Death Database including placental histopathology and standardised cause of death classification. Results . 952 stillbirths were included. The incidence of histopathological chorioamnionitis was 22.6%, with a bimodal distribution. A fetal inflammatory response was present in 10.1% and significantly correlated with spontaneous onset of labour. The absence of a fetal inflammatory response was strongly associated with unexplained antepartum death. Conclusions . The increased incidence of histological chorioamnionitis at extremes of gestation is confirmed in the largest dataset to date using population data. This has important implications for late gestation stillbirth as the percentage of unexplained stillbirths increases near term.