Four-dimensional and Doppler sonography in the diagnosis and surveillance of a true cord knot.

Prenatal diagnosis of a true knot of the umbilical cord is often an incidental observation at ultrasound with a difficult differential diagnosis between true and false knots. Furthermore, little is known about the optimal management of these cases. We report the importance of color Doppler and four-dimensional ultrasound for the differential diagnosis in the case of true cord knot and the role of Doppler flow velocimetry in the management of that case.