Umbilical cord
Amnionic web

Topic Completed: 1 July 2015

Minor changes: 20 February 2019

Copyright: 2002-2019,, Inc.

PubMed Search: Amnionic web

Paul J. Kowalski, M.D.
Page views in 2019: 687
Page views in 2020 to date: 559
Cite this page: Kowalski PJ. Amnionic web. website. Accessed August 11th, 2020.
Definition / general
  • Small portion of amniotic membrane can be present extending from the base of the umbilical cord and spanning the angle made by the fetal surface and the umbilical cord insertion
  • Amnion is the single layer of cuboidal to columnar cells that lines the entire amniotic cavity, including the fetal surface of the placenta and the umbilical cord
  • Amniotic web should be distinguished from an amniotic band, which is a congenital amniotic malformation that can result in serious constriction or entrapment of fetal parts (amniotic band syndrome or amniotic rupture sequence)
  • Uncommon finding, present in < 1% of uncomplicated live births
  • Amnion (and its underlying thin layer of amniotic mesoderm) is only loosely adherent to the adjacent chorion
  • This incompletely anchored nature of the amnion allows for incomplete investment of the acute angle made by the umbilical cord insertion and fetal surface
Clinical features
  • Generally an incidental finding with no clinical significance
  • Potential restriction of umbilical cord movement or constriction of vascular flow may be seen due to traction
Gross description
  • Translucent, delicate, sail-like portion of amnion spans the distance between a short segment of umbilical cord and the adjacent fetal surface
  • Retraction of the amnion can cause the umbilical cord to become tethered or anchored closely to the fetal surface
Gross images

Images hosted on other servers:
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Limited movement at the cord base

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Near term placenta

Differential diagnosis
  • Amniotic bands: consist of sheets or thicker strands / bands of amnion that can be found tethering any portion of the umbilical cord (not just its insertion site) or spanning between any portion of placenta and developing fetus
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