title: Correlation between cord insertion type and superficial choriovasculature in diamniotic-monochorionic twin placentas.
abstract: BACKGROUND
  Non-central cord insertion has been associated with diminished chorionic vascular distribution in singleton placentas. The choriovascular correlates of peripheral cord insertion in diamniotic-monochorionic twin placentas remain undetermined.
  
  
  OBJECTIVE
  To study the association between type of cord insertion and choriovascular distribution of both twin territories in diamniotic-monochorionic twin placentas.
  
  
  METHODS
  A prospective cohort of 138 monochorionic placentas was examined at Women and Infants Hospital between 2009 and early 2011. Thirty-five cases (25%), including disrupted placentas, placentas from higher order multiples and placentas from pregnancies complicated by twin-to-twin transfusion syndrome, were excluded. The correlation between cord insertion type and superficial choriovascular distribution was studied in the remaining 103 dye-injected diamniotic-monochorionic placentas. Cord insertion was categorized as paracentral, marginal or velamentous. The choriovascular distribution of each individual twin territory was assessed by analysis of number and density (number per surface area) of perforating chorionic arteries (PCA).
  
  
  RESULTS
  In contrast with singleton placentas, there was no correlation between cord insertion type and a twin's own choriovascular distribution in diamniotic-monochorionic placentas. However, a strong correlation was found between the choriovascular distribution of one twin and the cord insertion type of the opposite twin. For a twin with paracentral or marginal cord insertion, the PCA density was significantly higher if the co-twin had a velamentous cord insertion than if the co-twin had a paracentral cord insertion (P < 0.001 and P < 0.05, respectively). Similarly, the PCA density of a twin with velamentous cord insertion tended to be higher if the co-twin had a velamentous, rather than paracentral cord insertion (P = 0.09).
  
  
  CONCLUSIONS
  This is the first study to suggest that in diamniotic-monochorionic twin gestations, the choriovascular architecture correlates with the cord insertion type of the co-twin. In general, velamentous cord insertion is associated with expanded choriovascular distribution in the opposite twin territory. Our observations may reflect novel manifestations of twin interdependence in monochorionic pregnancies.
authors.affiliation: Department of Pathology, Women and Infants Hospital, Alpert Medical School of Brown University, Providence, RI 02905, USA. mdepaepe@wihri.org
authors.forename: M E
authors.initials: ME
authors.lastname: De Paepe
authors.forename: S
authors.initials: S
authors.lastname: Shapiro
authors.forename: L C
authors.initials: LC
authors.lastname: Hanley
authors.forename: S
authors.initials: S
authors.lastname: Chu
authors.forename: F I
authors.initials: FI
authors.lastname: Luks
mesh_terms: D000650:Amnion / Q000473:pathology; D002823:Chorion / Q000098:blood supply* / Q000473:pathology; D015331:Cohort Studies; D005260:Female; D005330:Fetofetal Transfusion / Q000473:pathology; D006801:Humans; D010920:Placenta / Q000033:anatomy & histology* / Q000098:blood supply / Q000473:pathology; D011247:Pregnancy; D011272:Pregnancy, Multiple / Q000502:physiology; D014427:Twins; D014430:Twins, Monozygotic; D014469:Umbilical Arteries / Q000033:anatomy & histology / Q000473:pathology; D014470:Umbilical Cord / Q000033:anatomy & histology* / Q000473:pathology