TRUE KNOT OF THE UMBILICAL-CORD - A DIFFICULT PRENATAL ULTRASONOGRAPHIC DIAGNOSIS

We examined retrospectively the use of ultrasonography in 18 cases in which a true knot of the umbilical cord was found at delivery. All wom en had a normal second-trimester scan in which no cord abnormality was detected. Thirteen (72%) also had third-trimester color Doppler ultra sonography, at which time the cord anomaly was again missed. In one of these cases the diagnosis could have been made with color flow imagin g, but the abnormal pattern was mistaken instead for multiple loops of cord. On the other hand, the diagnosis of true knot was considered pr enatally in two cases, but not confirmed at delivery, when only a prom inent false knot was found in one and a normal cord in the other. We c onclude that true knots of the umbilical cord do not have a characteri stic appearance in utero and therefore are easily missed at routine pr enatal ultrasonography.