Gross / macroscopic variations and conditions

Umbilical cord

Thin cord

Last author update: 1 June 2017
Last staff update: 19 May 2021

Copyright: 2002-2023,, Inc.

PubMed Search: Placenta thin cord

Paul J. Kowalski, M.D.
Page views in 2022: 1,339
Page views in 2023 to date: 554
Cite this page: Kowalski PJ. Thin cord. website. Accessed June 1st, 2023.
Definition / general
  • Decrease in the cross sectional diameter of the umbilical cord
  • Also called thin cord syndrome
Essential features
  • Due to a reduction in the amount and fluid content of supportive Wharton jelly, the number of umbilical vessels present or a combination of both
  • Cord diameter < 1.0 cm (normal: 1.25 - 2.5 cm) at term or an umbilical cord cross sectional area (on ultrasound examination) < 10th percentile for gestational age
  • Thin or lean umbilical cord should be distinguished from segmental thinning of an umbilical vessel, which is due to a paucity of the tunica media layer
  • Present in up to 10% of term infants, in some series
  • Reduction in Wharton jelly can predispose to compression of the umbilical vessels
  • Factors that determine the amount and content of Wharton jelly are poorly understood, although Wharton jelly typically increases until 32 weeks gestation and then slightly declines in fluid content thereafter
  • Reduction in the number of umbilical vessels is suggested to be due to atrophy of an umbilical artery
Clinical features
  • Associated with preeclampsia, intrauterine growth restriction and intrauterine fetal demise
  • Associated with fetal distress at the time of delivery (oligohydramnios, low Apgar scores and meconium stained amniotic fluid)
Case reports
Gross description
  • Umbilical cord diameter is measurably reduced
  • Lower coiling index (reduced number of spirals per unit length) may result in a hypocoiled gross appearance
Gross images

Images hosted on other servers:
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Fig C: comparative image
of a thin umbilical cord
(bottom) with a normal
diameter umbilical cord

Microscopic (histologic) description
  • Decrease in Wharton jelly can be appreciated
  • Umbilical vein may be diminished in size, while umbilical arteries appear normal in histologic appearance
Board review style question #1
Which of the following best describes a thin umbilical cord?

  1. A cord diameter less than 2 cm at term is characteristic
  2. A reduction in the size of the tunica media layer
  3. Associated with preterm labor
  4. No change in the number of umbilical vessels
  5. Predisposes the umbilical vessels to compression effects
Board review style answer #1
E. Thin cord is due to a decrease in Wharton jelly or a decrease in the number of umbilical vessels, which can predispose the umbilical vessels to compression phenomena.

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Reference: Thin umbilical cord
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