title: Acute histologic chorioamnionitis at term: nearly always noninfectious.
abstract: BACKGROUND
  The link between histologic acute chorioamnionitis and infection is well established in preterm deliveries, but less well-studied in term pregnancies, where infection is much less common.
  
  
  RESULTS
  We conducted a secondary analysis among 195 low-risk women with term pregnancies enrolled in a randomized trial. Histologic and microbiologic evaluation of placentas included anaerobic and aerobic cultures (including mycoplasma/ureaplasma species) as well as PCR. Infection was defined as ≥1,000 cfu of a single known pathogen or a ≥2 log difference in counts for a known pathogen versus other organisms in a mixed culture. Placental membranes were scored and categorized as: no chorioamnionitis, Grade 1 (subchorionitis and patchy acute chorioamnionitis), or Grade 2 (severe, confluent chorioamnionitis). Grade 1 or grade 2 histologic chorioamnionitis was present in 34% of placentas (67/195), but infection was present in only 4% (8/195). Histologic chorioamnionitis was strongly associated with intrapartum fever >38°C [69% (25/36) fever, 26% (42/159) afebrile, P<.0001]. Fever occurred in 18% (n = 36) of women. Most febrile women [92% (33/36)] had received epidural for pain relief, though the association with fever was present with and without epidural. The association remained significant in a logistic regression controlling for potential confounders (OR = 5.8, 95% CI = 2.2,15.0). Histologic chorioamnionitis was also associated with elevated serum levels of interleukin-8 (median = 1.3 pg/mL no histologic chorioamnionitis, 1.5 pg/mL Grade 1, 2.1 pg/mL Grade 2, P = 0.05) and interleukin-6 (median levels = 2.2 pg/mL no chorioamnionitis, 5.3 pg/mL Grade 1, 24.5 pg/mL Grade 2, P = 0.02) at admission for delivery as well as higher admission WBC counts (mean = 12,000 cells/mm(3) no chorioamnionitis, 13,400 cells/mm(3) Grade 1, 15,700 cells/mm(3) Grade 2, P = 0.0005).
  
  
  CONCLUSIONS
  Our results suggest histologic chorioamnionitis at term most often results from a noninfectious inflammatory process. It was strongly associated with fever, most of which was related to epidural used for pain relief. A more 'activated' maternal immune system at admission was also associated with histologic chorioamnionitis.
authors.affiliation: Department of Pathology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, United States of America.
authors.forename: Drucilla J
authors.initials: DJ
authors.lastname: Roberts
authors.forename: Ann C
authors.initials: AC
authors.lastname: Celi
authors.forename: Laura E
authors.initials: LE
authors.lastname: Riley
authors.forename: Andrew B
authors.initials: AB
authors.lastname: Onderdonk
authors.forename: Theonia K
authors.initials: TK
authors.lastname: Boyd
authors.forename: Lise Carolyn
authors.initials: LC
authors.lastname: Johnson
authors.forename: Ellice
authors.initials: E
authors.lastname: Lieberman
mesh_terms: D000208:Acute Disease; D002821:Chorioamnionitis / Q000175:diagnosis* / Q000209:etiology*; D005260:Female; D006801:Humans; D011247:Pregnancy; D011251:Pregnancy Complications, Infectious / Q000175:diagnosis; D011379:Prognosis; D012307:Risk Factors