The umbilical arteries arise within fetal circulation from the common iliac arteries and represent the dominant circulatory outflow of the distal aortic circulation and contribute entirely to placental circulation. Normal umbilical artery resistance to blood flow progressively decreases throughout pregnancy, reflecting the progressive increase in placental mass and the increased numbers of tertiary villous small vessels of the placenta [7]. Doppler ultrasonography is a noninvasive technique that is used to assess the hemodynamic components of vascular impedance within the placenta. Umbilical artery Doppler flow velocimetry has been developed to evaluate fetal condition en-utero [8]. Normally developing and growing fetuses are characterized by high velocity diastolic umbilical artery flow, while those with IUGR have decreased, absent, or reversed diastolic flow [9,10]. Abnormal umbilical artery flow has been defined as the presence of absent or reversed end diastolic flow or a flow index greater than two standard deviations above the reported mean flow index for a given gestational age [11,12]. Evaluation of umbilical artery hemodynamics is indicated as part of standard care when IUGR or significant fetal anemia due to iso-immunization is suspected [7,8].