Placenta extrachorialis

Morphological abnormality of the placenta in which transition from a membranous to villous chorion does not occur at the placental edge but at some variable distance within the circumference of the placenta.

  • Chorionic plate (fetal side) is smaller than the basal plate (maternal side)


There are 2 types of extrachorial placenta:
  1. Circummarginate placenta. Margin of chorionic plate appears as a raised, thin fibrous rim at the margin of the chorionic plate where the fetal vessels appear to terminate.
  2. Circumvallate placenta. Thickened membranous rim, composed of a double fold of amnion and chorion with degenerated decidua and fibrin in between, is folded inward towards the center.


  • Intrauterine growth restriction (IUGR)
  • Antepartum haemorrhage (APH)
  • Retained placenta

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