ENTANGLED UMBILICAL CORDS IN

MONOCHORIONIC MONOAMNIOTIC TWINS

• Cord entanglement is found in up to 71% of monochorionic twin pregnancies (1).
• Over 50% of deaths in monochorionic twin pregnancies have been attributed to cord entanglement (1,2).
• Cord entanglement is thought to be caused by normal fetal movements. It probably occurs early in pregnancy when the ratio of the amniotic cavity to fetal size is the largest, and fetal movements relative to each other are the greatest.

ULTRASOUND

• Apparent branching of the umbilical arteries (>20 weeks GA).
• Branching Y sign (4). This sign depends on the visualization of individual umbilical arteries, which have different heart rates on color doppler, as well as a different S/D ratio on pulsed doppler. This may not be practical in the first trimester as the vessels are too small and end diastolic flow is not yet present.
• Two distinct arterial wave patterns due to different heart rates within the sample gate. This is indicative of both monoamnionicity and cord entanglement (5).
• Do not confuse with clustering of single segments of a single umbilical cord (stack of coins appearance).

• Loops of cord crossing each other but no entanglement.

OUTCOME

• Does not imply impending fetal demise, however it does place the fetus at high risk for an impending vascular accident.

REFERENCES

1. Baldwin VJ. Pathology of Multiple Pregnancy. New York, Springer-Verlag, 1994.
2. Lumme RH, Saarikoski SV. Monoamniotic twin pregnancy. Acta Genet Med Gemellol 1986;35:99-105.
3. Townsend RR, Filly RA. Sonography of noncojoined monoamniotic twin pregnancies. J Ultrasound Med 1988;7:665.
4. Belfort MA, Moise KJ Jr, Kirshon B et.al. The use of color flow doppler ultrasonography to diagnose umbilical cord entanglement in monoamniotic twin gestations. Am J Obstet Gynecol 1993;168:601-604.
5. Overton TG, Denbow ML, Duncan KR et.al. First trimester cord entanglement in monoamniotic twins. Ultrasound Obstet Gynecol 1999;13:140-142.