nuchal cord

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°.

Epidemiology

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 . Overall prevalence tends to increase with advancing gestational age. There may be an increased male predilection.

Pathology

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%).

Classification

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

• 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

Associations

• long umbilical cord
• polyhydramnios

Radiographic features

Antenatal ultrasound

• on gery-scale ultrasound may show a small dent or impression due to compression of the fetal neck posteriorly on sagittal plane may also be present (termed the grey-scale divot sign )
• may be seen as a persisting structure wrapped around the fetal neck with color flow present on Doppler interrogation
• color Doppler also helps to assess single or multiple turns of nuchal cord in sagittal section 

Treatment and prognosis

Some advocate immediate and repeated fetal testing measures should be sought when further complicating issues are confronted.

Complications

• formation of a cord knot
• tight cord around the neck syndrome (tCAN syndrome) 
• intrauterine growth restriction (IUGR)
• fetal developmental delay
• decreased amniotic fluid volumes
• neonatal anemia
• decreased fetal movements
• hypovolemia and metabolic acidosis 
• post dates
• in rare situations, intrauterine fetal death

Differential diagnosis

For extra tissue around the fetal neck on ultrasound consider:

• cystic hygroma: no color flow
• redundant uncoiled cord adjacent to the fetal neck 

Siehe auch:

• zystisches Lymphangiom
• Nabelschnur

und weiter:

• umbilical cord entanglement
• long umbilical cord