o_1977r8vv9vk1ts2ms0kd8pksa.pdf

a Chapter 13 Cerebral and Umbilical Doppler in the Prediction of Fetal Outcome 193
Fig. 13.16. a Umbilical cord
compression. Variations in percentage
from the pre-test value
of the: Heart rate (HR), umbilical
vascular resistances (URI), umbilical
flow (UBF), cerebral±umbilical
ratio (C/U), fetal pO 2 , and
cerebral flow (CBF) during a
period of chord compression.
The C/U decreases in proportion
with the fetal pO 2 and the
UBF, whereas CBF remains unchanged.
b Aortic compression.
Variations in percentage from
the pre-test value of the HR,
URI, UBF, C/U, fetal pO 2 , and
CBF during a period of chord
compression. The C/U decreases
in proportion with the fetal
pO 2 , whereas the UBF and CBF
remain unchanged. c Relationship
between absolute values
of the C/U ratio and the pO 2
during induced hypoxia
Cerebral flow changes in relation to hypoxia and
fetal distress continues to be one of the most interesting
areas of investigation. Even though many studies
have already demonstrated positive correlations between
cerebral Doppler data and fetal hypoxia or fetal
well-being, it is too early to draw a conclusion as to
how to use cerebral Doppler studies in routine practice
for the management of fetal distress and for
making the decision to interrupt a gestation.
The C/U, which measures the proportion of flow
supplying the brain and the placenta, is now the most
widely used parameter for the assessment of IUGR
and hypoxia. Firstly, it takes into account the causes
and consequences of the placental insufficiency responsible
for IUGR and hypoxia. Secondly, it is not
heart-rate dependent. Thirdly, it has a single cut-off
value (C/U is normal if > 1.1), at least during the second
half of the pregnancy. On the other hand, be-