Knowledge of the development, normal sonographic appearance, and poten
tial abnormalities of the umbilical cord is important in fetal assessm
ent, The umbilical cord can be visualized throughout most of gestation
and is detectable sonographically soon after visualization of the fet
al pole, The normal umbilical cord is 50-60 cm long and may coil as ma
ny as 40 times, usually to the left, Abnormalities in umbilical cord s
ize, degree of coiling, attachment, and position can have important im
plications for the outcome of the pregnancy, Structural abnormalities
of the umbilical cord such as single umbilical artery, knots, cysts, a
nd tumors may be associated with fetal distress or malformations, Colo
r Doppler ultrasound (US) is useful in the identification and evaluati
on of structural abnormalities of the cord, By allowing measurement of
blood flow velocity in the umbilical artery, duplex Doppler US may pr
ovide additional information in the evaluation of intrauterine growth
retardation and twin-twin transfusion syndrome.