Gross/Macroscopic Variations and Conditions
Umbilical cord
Marked segmental thinning

Topic Completed: 1 January 2017

Minor changes: 28 October 2020

Copyright: 2002-2020,, Inc.

PubMed search: Marked segmental thinning

Paul J. Kowalski, M.D.
Page views in 2019: 165
Page views in 2020 to date: 202
Cite this page: Kowalski PJ. Marked segmental thinning. website. Accessed December 4th, 2020.
Definition / general
  • Focal thinning of an umbilical vessel due to the (near) absence of tunica media layer
Essential features
  • Umbilical vein is usually affected in the majority (75%) of cases, with the umbilical arteries affected in the minority (25%) of cases
  • In affected vessels, the tunica media in at least one cord level is absent but usually less than 30% of the circumference of the affected level shows absent media
  • Similar changes can be seen in the placental stem vessels
  • Segmental thinning of an umbilical vessel should be distinguished from a thin umbilical cord, which is due to variable loss of supportive Wharton jelly in an affected segment of umbilical cord
  • Approximately 1.5% of term placentas are affected
  • Unknown
  • Unknown
Clinical features
  • Can be seen in association with fetal distress or congenital anomalies, such as cerebral palsy, anencephaly or urinary tract abnormalities
Gross description
  • No gross abnormality is usually seen
Microscopic (histologic) description
  • Affected vessel wall typically appears thin with (virtually) complete loss of the muscular tunica media layer
Additional references
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