True umbilical cord knot

True umbilical cord knots are a rare occurrence and as the name suggests represent a knot formation in the umbilical cord.

They occur in less than 1% of pregnancies.

Predisposing factors
Ultrasound
  • focal dilatation of umbilical vein or umbilical vein thrombosis near the umbilical cord knot- giving a false appearance of an umbilical cord cyst.
  • tortuosity of cord at level of knot
  • a segment of umbilical cord that is closely surrounded by another loop of umbilical cord is considered to be highly specific of a true knot and is known as hanging noose sign

Most of the knots formed in the umbilical cord are loose and thereby do not adversely impact the fetal well being; however due to fetal movement or descent the knot could get tighter, thereby decreasing the umbilical cord blood flow. This could further lead to fetal asphyxia and demise.

Ultrasound - obstetric
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Article information

rID: 38507
System: Obstetrics
Tag: refs
Synonyms or Alternate Spellings:
  • True knot in umbilical cord
  • True knot of the cord
  • True knot
  • True umbilical cord knots
  • True knots

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