Nuchal cord

Last revised by Ashesh Ishwarlal Ranchod on 10 Sep 2023

Nuchal cord is a term given to the situation where there are one or more loops of umbilical cord wrapped around the fetal neck for ≥360°.

The prevalence is dependent on the extent of coiling and ranges from ~25% for a single loop, to 2.5% for a double loop, to ~0.5% for more than two loops 1,2. Overall prevalence tends to increase with advancing gestational age. There may be an increased male predilection.

The etiology of nuchal cords is controversial and unclear. Some suggest that fetuses with nuchal cords have less vascular coiling than those that do not (65%). 

According to the Giacomello classification system, a nuchal cord can be of two types 4,8:

  • type A: a nuchal loop that encircles the neck in a freely sliding pattern, where the placental end crosses over the umbilical end; this pattern can undo itself

  • type B: a nuchal loop that encircles the neck in a locked pattern, where the placental end crosses under the umbilical end; this pattern locks and cannot undo itself with potential for fetal morbidity or mortality

  • on grey-scale ultrasound in the sagittal plane, there may be a small dent or impression of the posterior fetal neck due to compression from the cord (termed the grey-scale divot sign 10)

  • the cord can be seen as a persistent structure wrapped around the fetal neck with color Doppler flow

  • color Doppler also helps to assess single or multiple turns of nuchal cord in the sagittal plane

Some authors advocate immediate and repeated fetal testing measures when complications are present.

The Terminologia Anatomica refers to the neck as a whole as the "collum". In official Latin anatomical nomenclature, "cervix" refers to the front of the neck and "nucha" to the back (nape) of the neck 12

For extra tissue around the fetal neck on ultrasound consider:

  • cystic hygroma: no color flow

  • redundant uncoiled cord adjacent to the fetal neck 

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