title: Placental cavities.
abstract: OBJECTIVE
  To study placental cavities by gross and microscopic examination and ultrasonography and their frequency with various epidemiologic factors and intervillous thrombosis.
  
  
  METHODS
  After formalin fixation, interval sections of 567 placentas were prepared to search for cavities and intervillous thrombosis. Cavities were subjected to histologic and ultrasonographic examinations.
  
  
  RESULTS
  Frequency of cavities with diameter of 1 cm or more was 34.9% in 567 mature placentas. Frequency of cavities was significantly higher in heavy, thick placentas associated with male fetuses. Histologic examination revealed villus laceration in cavities and syncytial cells, isolated chorionic villi, or air bubbles in placental fetal veins. All 82 placentas with cavities showed villus lacerations in the cavities and air bubbles in the fetal veins. Intervillous thromboses in fetal lobules were located only in the cavities. Cavities were first found by ultrasonography at a mean gestational age of 30.9 +/- 3.8 weeks. Ultrasonography did not always differentiate accurately between intervillous thrombosis and cavities.
  
  
  CONCLUSIONS
  Placental cavities were found significantly more often in heavy, thick placentas associated with male fetuses. Strong uterine contractions during placental detachment could produce villus laceration in cavities, following contamination by air bubbles and isolated villus tissue in the fetal veins. Placental cavities are vulnerable to villus laceration. Intervillous thrombosis occurred only in cavities.
authors.affiliation: Department of Pathology, Keio University, School of Medicine, Tokyo and Sho Hospital, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Fujikura
authors.forename: S
authors.initials: S
authors.lastname: Sho
mesh_terms: D005260:Female; D006801:Humans; D008297:Male; D009929:Organ Size; D010920:Placenta / Q000033:anatomy & histology* / Q000473:pathology*