Umbilical cord
Amnionic web

Author: Paul J. Kowalski, M.D. (see Authors page)

Revised: 17 October 2017, last major update July 2015

Copyright: (c) 2002-2017,, Inc.

PubMed Search: Amnionic web

Cite this page: Kowalski, P.J. Amnionic web. website. Accessed November 15th, 2018.
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:
Missing Image

Limited movement at the cord base

Missing Image

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