A nuchal cord (NC) is a term given to 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 range 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%).
The Giacomello classfication system , a nuchal cord be can be of two types 4,8.
- type I (a): can spontaneously unwind
- type II (b): cannot spontaneously unwind (locking type)
It may be seen as a persisting structure wrapped around the fetal neck with colour flow present on Doppler interrogation. A appearance of a small dent or impression due to compression of the fetal neck may also be present (termed the divot sign)
- formation of a cord knot
- intra uterine growth restriction (IUGR)
- fetal developmental delay
Some advocate immediate and repeated fetal testing measures should be sought when further complicating issues are confronted, such as:
- significantly decreased amniotic fluid volumes
- post dates
- fetal growth restriction
- decreased fetal movements
For extra tissue around the fetal neck on ultrasound consider:
- cystic hygroma: no colour flow
- redundant uncoiled cord adjacent to the fetal neck
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