o_1977r8vv9vk1ts2ms0kd8pksa.pdf

344 A. Lysikiewicz
Fig. 22.5. Fetal preload index and fetal
hematocrit at cordocentesis
Changes in Fetal Venous Blood Flow
High arterial fetal blood flow velocity and increased
tissue perfusion in the fetal hyperdynamic cardiovascular
state is followed by a blood volume shift from
arterial to venous circulation resulting from decreased
blood viscosity [40]. The resulting high venous
return may lead to right heart overload and
right heart failure that can be detectable by Doppler
velocimetry [41]; therefore, fetal venous flow has been
extensively studied as an indicator of fetal condition
in alloimmunization.
Umbilical Vein
An early study by Jouppila reported an inverse correlation
between umbilical venous flow and fetal hemoglobin
at birth within 4 days from delivery [42]. It
was later confirmed by Warren et al. [40] and Iskaros
et al. [6] who noted increased venous blood flow in
the umbilical vein associated with development of fetal
hydrops. Dukkler et al. [39] attempted to correlate
intrahepatic umbilical venous maximum velocity and
MCA peak velocity with fetal anemia in six fetuses
with alloimmunization. They found that in prediction
of fetal anemia, the MCA was 100% specific, while intrahepatic
umbilical venous blood flow had specificity
of 83%.
Inferior Vena Cava Blood Flow
Inferior vena cava blood flow has been described as
the A/S index or the atrial flow velocity to atrial regurgitation
velocity ratio (Fig. 22.5) [41]. This index
Fig. 22.6. Inferior vena cava A/S ratio
is a sensitive indicator of the right cardiac function,
especially fetal right heart failure.
In fetal hyperdynamic circulation in anemic fetuses
with isoimmunization, an increased venous return
could lead to right heart failure. Studies of inferior
vena cava blood flow do not, however, support
this assumption. In an early study by Rightmire et al.
[27] inferior vena cava average velocity was elevated
prior to the first blood transfusion in anemic fetuses,
but the correlation with fetal hematocrit was not significant.
In our own series, 20 fetal preload index
measurements were followed by fetal hematocrit evaluations
by immediate cordocentesis in 13 fetuses in
alloimmunized pregnancies (Fig. 22.6) [43]. An asso-