Knotting on heaven’s door: 3D color Doppler ultrasound imaging of a true cord knot

Excerpt

Although rare, true umbilical cord knot (TUCK) can be found in about 0.3–2.1 % of all births [1]. This condition seems to be more frequent in case of polyhydramnios, gestational diabetes, small fetus, long umbilical cord and amniocentesis [2]. Considering the data published so far, TUCKs are associated with higher rate of fetal death respect to general obstetric population, and may cause an altered fetal heart pattern at cardiotocogram which often lead to cesarean section [1]. To date, modern ultrasound equipment allows the identification of a TUCK, even if it is possible that it may pass unnoticed to routine scan. Starting from the normal gray-scale cross section of umbilical cord, a circular cord loop should raise suspicion and suggest further investigation. In this case, 3D color Doppler ultrasound imaging of the suspected umbilical cord section can confirm the diagnosis (Fig. 1). Moreover, cord compression in a constricted knot may cause altered pulsed Doppler velocimetry of the umbilical vessels [3] and notching in the umbilical artery waveform [4], which further help to confirm the diagnosis. Recent data [5] suggested that TUCK does not contribute to prenatal morbidity and mortality in monoamniotic twin pregnancies. Nevertheless, robust evidence about maternal-fetal outcomes in case of TUCK is still lacking. Considered this last point, which underlies the necessity of large case series and/or meta-analysis about this condition, we suggest performing 3D color Doppler and pulsed velocimetry evaluation in case of suspected TUCK, and a close monitoring of the pregnancy, labor and delivery.

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