Umbilical cord entanglement

Umbilical cord entanglement is a feature which can mean either one or more loops of the umbilical cord encircling any part of the fetal body or two umbilical cords becoming entangled with each other ³. In the latter situation, it is a classical feature of a monochorionic-monoamniotic twin pregnancy.  Very rarely it can occur in a diamniotic twinning with disruption of the dividing membrane either naturally or secondary to a procedure such as an amniocentesis.

Epidemiology

It is often considered a part of normal early fetal development and can be a common finding in the 1^st trimester. It has been described in over 70% of MCMA twin pregnancies and it is less of a problem in very early pregnancy.

Radiographic features

Ultrasound 

If an associated tightening/knot is a concern Doppler assessment can be carried out.

Doppler assessment

If there is problematic flow due to cord entanglement there may be evidence of abnormal RI's and S:D ratios, the presence of diastolic notching and reduction in end-diastolic flow in umbilical arterial Doppler assessment and pulsatile waveforms in umbilical venous flow assessment.

Significance

Cord entanglement itself is rarely a problem but an associated tightening leading to an umbilical cord knot is a concern where arterial compromise can cause catastrophic complications.

Differential diagnosis

Considerations in ultrasound include

• true or false umbilical cord knot in one twin

See also

• umbilical cord knot
• nuchal cord