title: A new, clinically oriented, unifying and simple placental classification system.
abstract: OBJECTIVE
  At present there is no internationally accepted, clinically easy understandable, comprehensive morphological placental classification. This hampers international benchmarking and comparisons, and clinical research.
  
  
  METHODS
  Internationally published criteria on morphological placental pathology were collected, standardized and focused into a comprehensive diagnosis category system. The idea was to create a clinically relevant placental pathology scheme related to major pathological processes. A system of nine main diagnostic categories (normal placenta included) was constructed. Pathologists and obstetricians discussed the mutual understanding of the wording in the reporting. The previously published diagnostic criteria were merged, structured and standardized. Through an interobserver correlation study on 315 placentas from intrauterine deaths and 31 controls (placentas from live births) the microscopic criteria in this classification system were tested on user-friendliness and reproducibility.
  
  
  RESULTS
  The clinical feedback has been very positive, focusing on the understandability and usefulness in patient follow-up. The interobserver agreement in the microscopic correlation study was in general good. The differences in agreement mainly reflected the degree of preciseness of the microscopic criteria, exemplified by excellent correlation in diagnosing acute chorioamnionitis. Maternal and fetal circulatory disorders need grading criteria and studies are needed to get more insight and clinical correlations of villitis and maturation disorders.
  
  
  CONCLUSIONS
  The clinically oriented, unifying and simple placental pathology classification system may work as a platform for standardization and international benchmarking. Further research is needed to define diagnostic criteria in staging and grading of some main diagnostic categories.
authors.affiliation: Department of Pathology, Oslo University Hospital (OUS), Oslo, Norway. g.e.turowski@medisin.uio.no
authors.forename: G
authors.initials: G
authors.lastname: Turowski
authors.forename: L N
authors.initials: LN
authors.lastname: Berge
authors.forename: L B
authors.initials: LB
authors.lastname: Helgadottir
authors.forename: E-M
authors.initials: EM
authors.lastname: Jacobsen
authors.forename: B
authors.initials: B
authors.lastname: Roald
mesh_terms: D005260:Female; D005313:Fetal Death / Q000473:pathology; D006785:Hospitals, University; D006801:Humans; D050498:Live Birth; D009664:Norway; D015588:Observer Variation; D010920:Placenta / Q000033:anatomy & histology* / Q000473:pathology*; D010922:Placenta Diseases / Q000175:diagnosis / Q000473:pathology*; D017410:Practice Guidelines as Topic; D011247:Pregnancy; D011262:Pregnancy Trimester, Second; D011263:Pregnancy Trimester, Third; D012189:Retrospective Studies; D009626:Terminology as Topic