The assessment of fetal well-being by venous Doppler velocimetry

Abstract

The assessment of fetal well-being by venous Doppler velocimetry, especially in cases of intrauterine growth restriction, has been growing in importance as a number of researchers have been improving their studies 1 -5 as well as a consequence of better technologies in ultrasound equipment. Since different authors have studied the fetal blood circulation with color Doppler, initially focusing their attention on the arterial system 6 -12 , many questions and doubts have remained without a reasonable answer, especially concerning the optimal time at which to deliver these fetuses. Among these authors, some have expressed the opinion that all biophysical methods, including the cardiotocogram, should be used before the decision of fetus delivery should be made 13,14 . It is possible, nowadays, to study several venous vessels, such as the ductus venosus, inferior vena cava, umbilical vein, portal vein, hepatic veins 15 , and, more recently 1,2 , the cerebral transverse sinus. The purpose of this review is to describe the fetal circulation, the technique and rationale behind measuring venous Dopplers and to assess the clinical applications of venous Doppler velocimetry.

The development, structure and blood flow within the umbilical cord with particular reference to the venous system

“…due to foetal breathing movements causing a pressure gradient between the umbilical vein and the ductus venosus 30 such that there is an increase in the velocity of the blood in the umbilical vein during inspiration. 33 2 Passive pressure changes in the umbilical cord vein due to longitudinal distortion of the arteries with each foetal heart beat. The pressure peaks in the umbilical cord artery and vein are out of phase by 180° which results in the addition of the effect of numerous, small pressure changes along the length of the cord and the subsequent movement of blood through the umbilical cord vein.…”

Doppler Assessment of the Intrauterine Growth‐Restricted Fetus

“…Deterioration of fetal hypoxemia leads to the decompensatory stage. This stage is characterized by the incipient heart failure leading to the reverse flow in UA and MCA and disappearance of the “brain‐sparing effect.” This hemodynamic pattern is associated with severe abnormalities involving several fetal organ systems 9–11 …”

“…Resuming the Venous Doppler changes in IUGR after the decompensatory stage, we can observe decrease or reverse flow at the DV, increase at the reverse flow at the IVC, and UV pulsations. These alterations are presented when there is a severe deterioration of hypoxemia and may be of great clinical significance in deciding the timing of delivery 11 …”