Objectives: We investigated the incidence and outcome of clinical and histological chorioamnionitis (CA) and the associated risk factors in an emerging provincial perinatal center in 2014-2015.Study design: Based on the suspected and proven clinical infection in the third trimester of pregnancy, placenta and accessories from singleton deliveries were routinely examined histologically. The incidence of CA and associated fetal and neonatal outcome were compared by the total deliveries.Results: Of the 14,166 deliveries in 12 months, infection and inflammation were found in 373 out of 2372 (15.7%) placentas subjected to histological examination and diagnosed as CA (2.6%). These cases were divided into four groups as histological CA only (HCA, n = 335), clinical and histological CA (HCC, n = 20), clinical CA only (CCA, n = 18) and non-CA control (CON, n = 1999). Thus, an incidence of histological CA was 2.5% (355/14 166) in this birth population. Compared to CON, HCA group was more likely to have premature rupture of membrane, antenatal antibiotic use, gestational age <34 weeks, fetal distress, positive bacterial culture from vaginal secretions, and early-onset sepsis in newborns (all p ≤ .01), which were associated with perinatal risk factors of CA. In the very preterm subgroups, more stillbirths and death at delivery and neonatal intensive care unit admissions (p < .001) were found in the CA group.Conclusions: The results suggested that histological CA was associated with early-onset sepsis and combined perinatal comorbidities which are of more diagnostic importance than clinical only CA. The placental histological examination should be routinely performed in very preterm births to better assess perinatal and neonatal outcome.

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