Placenta
Umbilical cord
Nuchal cord

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

Revised: 13 March 2016, last major update March 2016

Copyright: (c) 2002-2016, PathologyOutlines.com, Inc.

PubMed Search: Nuchal cord [title]
Definition / General
  • An umbilical cord that becomes wrapped around the baby's neck at some point during gestation
Terminology
  • Single nuchal cord is defined as an umbilical cord that loops once around the neck
  • Two nuchal cords (a double nuchal cord) occurs when two loops of umbilical cord are wrapped around the neck
  • Three nuchal cords (a triple nuchal cord) occurs when three loops of umbilical cord are wrapped around the neck
  • Nuchal cords can be qualitatively described as loose (no constriction) or as mildly, moderately or severely tight/constricting
Epidemiology
  • Increased risk in extremely long umbilical cords
  • Increased risk in twin or multiple gestations
  • A single nuchal cord is present in approximately 20% of term deliveries
  • Two nuchal cords and three nuchal cords occur in 2.5% and 0.5% of term deliveries, respectively
Pathophysiology
  • If the umbilical cord begins to constrict around the neck, vascular occlusion of the umbilical vessels and subsequent decreased venous return from the placenta can lead to asphyxia
  • In type A nuchal cord, the placental end of the umbilical cord crosses over the fetal end, allowing the ability for the nuchal cord to undo itself in time (an 'unlocked' nuchal cord)
  • In a type B nuchal cord, the placental end of the umbilical cord crosses under the fetal end, negating the ability for the nuchal cord to undo itself in time (a 'locked' nuchal cord)
Etiology
  • Fetal movement dynamics in utero can cause entanglement of the umbilical cord around fetal body parts, such as the fetal neck
Clinical Features
  • A tight nuchal cord can compress the underlying fetal skin (the 'divot' sign)
  • Nuchal cords are associated with fetal growth restriction, poorer long term neurologic outcomes, cerebral palsy, increased admissions to the intensive care unit, increased rate of cesarean delivery and fetal demise
Diagnosis
  • Prenatal or postnatal identification
Radiology Images
  • Doppler ultrasound evaluation can identify a persistent structure wrapped around the fetal neck
Prognostic Factors
  • The vast majority of single nuchal cords are not associated with adverse perinatal outcomes
  • Type B (locked pattern) nuchal cords have a greater significance in terms of clinical outcome
Gross Description
  • Identify the number of loops around the neck and provide a qualitative assessment of constriction, if present (from Obstetrics)
  • In excessively long umbilical cords, nuchal cords can co-exist with true knots
  • Usually no gross abnormalities are present (after the umbilical cord and placenta have been received from Obstetrics), but examine the cord for any associated abnormalities, such as hemorrhage, hematoma, thrombosis or stricture
Gross Images

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Nuchal cord

Micro Description
  • Usually no significant histopathologic abnormality present, unless accompanied by some type of secondary pathology