title: Chronic chorioamnionitis is the most common placental lesion in late preterm birth.
abstract: OBJECTIVE
  The pathogenesis of late preterm birth remains elusive for the mechanisms of disease responsible. Placental examination can often provide important clues for the pathogenesis of pregnancy complications. This study was conducted to determine placental pathologic findings according to the gestational age and the clinical circumstances of preterm birth.
  
  
  METHODS
  Placental pathologic findings and obstetrical and neonatal outcomes were reviewed in a consecutive preterm birth cohort from a single tertiary center (N = 1206). Placentas of term births (N = 300) were used as normal controls.
  
  
  RESULTS
  Acute chorioamnionitis (22.7% vs. 16.7%), maternal vascular underperfusion (6.4% vs. 0.5%), and chronic chorioamnionitis (20.8% vs. 10.5%) were significantly more frequent in preterm births than in term births (P < 0.05, for each). Among preterm births, chronic chorioamnionitis was the most common pathology of late preterm birth (gestational age <37 and ≥34 weeks), while acute chorioamnionitis was the most common lesion of extremely preterm birth (gestational age <28 weeks). While the frequency of acute chorioamnionitis decreased with advancing gestation, that of chronic chorioamnionitis increased (P < 0.001, for each). The upward trend of the frequency of chronic chorioamnionitis was related to advancing gestation in both spontaneous and indicated preterm births (P < 0.001, for each).
  
  
  CONCLUSIONS
  Chronic chorioamnionitis is a common pathology of late preterm birth. It is suggested that chronic chorioamnionitis, a feature of maternal anti-fetal rejection, is an important etiology of preterm birth, especially of late preterm birth.
authors.affiliation: Department of Obstetrics and Gynecology, Seoul National University College of Medicine, 28 Yeongeon-dong, Chongno-gu, Seoul 110-744, Republic of Korea. doctor-joon@hanmail.net
authors.forename: J
authors.initials: J
authors.lastname: Lee
authors.forename: J-S
authors.initials: JS
authors.lastname: Kim
authors.forename: J W
authors.initials: JW
authors.lastname: Park
authors.forename: C-W
authors.initials: CW
authors.lastname: Park
authors.forename: J S
authors.initials: JS
authors.lastname: Park
authors.forename: J K
authors.initials: JK
authors.lastname: Jun
authors.forename: B H
authors.initials: BH
authors.lastname: Yoon
mesh_terms: D000328:Adult; D002821:Chorioamnionitis / Q000473:pathology*; D002908:Chronic Disease; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D010920:Placenta / Q000473:pathology*; D011247:Pregnancy; D047928:Premature Birth / Q000209:etiology*