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Chapter 24
Doppler Velocimetry for Fetal Surveillance:
Adverse Perinatal Outcome and Fetal Hypoxia
Dev Maulik, Reinaldo Figueroa
The primary objective of fetal surveillance is to detect
fetal compromise arising from nutritive and respiratory
deficiencies. A variety of obstetric complications,
including fetal growth restriction and hypertension,
may expose the fetus to such risks. There is emerging
evidence that the growth-restricted human fetus suffers
from chronic hypoxia and acidosis. Although an
immense amount of information is available on acute
and subacute fetal respiratory deficit, the mechanism
of chronic nutritional and respiratory deficiency in
the fetus has remained relatively ill-understood.
Encountering unfavorable circumstances, the fetus
appears to mobilize a spectrum of compensatory responses,
including preferential preservation of fetal
growth over placental growth, changes in fetal movement
pattern, and eventual deceleration of the fetal
growth rate (Fig. 24.1). In the face of deepening deprivation,
compensation gives way to decompensation.
It has also been shown that a central component
of the fetal homeostatic response involves flow redistribution,
which favors the vital organs (i.e., brain,
heart, adrenals), whereas flow to muscle, viscera,
skin, and other less critical tissues and organs declines
[1]. Underlying this phenomenon are the diverse
changes in impedance in these vascular systems.
The introduction of Doppler velocimetry has not
only enabled us to investigate this phenomenon in
the human fetus but it has opened up the potential of
its use for detecting fetal compromise. A significant
amount of information exists on the diagnostic efficacy
of the Doppler method for identifying the fetus
with adverse outcome as defined by various clinical
parameters. What constitutes adverse perinatal outcome,
however, is a highly controversial and problematic
issue. It is well recognized that many of these
Fig. 24.1. Summary of fetal sequential response
to progressive stress. Note that
the depicted sequence is an approximation;
the actual course may vary depending
on the characteristics of the chronic
deprivation and the individual fetal ability
to cope