o_1977r8vv9vk1ts2ms0kd8pksa.pdf

372 D. Maulik, R. Figueroa
ing indicators of fetal well-being: fetal heart rate
variability, body movements, breathing movements,
and Doppler hemodynamic evaluation of the umbilical
and internal carotid arteries. The study population
consisted of 19 SGA fetuses who eventually required
delivery by cesarean section because of fetal
distress. In 14 of 19 fetuses, abnormal velocity waveforms
were present from the beginning of the study.
The heart rate variability was initially marginal but
declined further during the last 2 days preceding delivery.
Decreased body and breathing movements occurred
subsequently and less frequently. The worst
outcome was in fetuses with reversed end-diastolic
velocities and a rapid fall in the variability. The
authors concluded that with the progressive decline
of the fetal condition fetal test abnormalities occur in
the following sequence: Abnormal velocity waveform
patterns occur first followed by a progressive decrease
in the heart rate variability; fetal general body
and breathing movements are the last to decline.
Weiner et al. [34], studying hemodynamic changes
in the middle cerebral artery and the aortic and pulmonic
outflow tracts, correlated these changes with
the computerized fetal heart rate pattern in fetuses
with absent end-diastolic velocity in the umbilical artery.
They observed that with progressive deterioration
of the fetal status the cerebral circulation loses
its autonomic reactivity first, followed within a few
days by a similar response in the heart, as shown by
the decreased fetal heart rate variability. This study is
discussed in greater detail in Chap. 25.
A prospective longitudinal study was conducted by
Hecher et al. [35] that included short-term variation
of the fetal heart rate, PIs of fetal arterial and venous
waveforms, and the amniotic fluid index. The study
population included 110 singleton pregnancies with
growth-restricted fetuses after 24 weeks of gestation
and was divided into two groups: pregnancies delivered
at 32 weeks or less and pregnancies delivered
after 32 weeks. The first variables to become abnormal
were the amniotic fluid index and the umbilical
artery PI. Abnormalities of the middle cerebral artery,
aorta, fetal heart rate short-term variation, ductus venosus,
and inferior vena cava then followed. The decrease
in PI of the middle cerebral artery followed
the abnormalities in the umbilical PI, and became
progressively abnormal until delivery in the pregnancies
delivered before 32 weeks. In pregnancies delivered
after 32 weeks the authors found a normalization
of the middle cerebral artery PI before abnormalities
in the fetal heart rate. In the pregnancies delivered
before 32 weeks of gestation, the increase in
the ductus venosus PI and the decrease in short-term
variation were more pronounced than the changes in
the other variables and became abnormal a few days
before delivery. In addition, perinatal mortality was
significantly higher if the short-term variation and
ductus venosus PI were abnormal compared to only
one or neither being abnormal.
Baschat et al. [36] examined longitudinally 44
growth-restricted fetuses with elevated umbilical artery
PI (> 2 standard deviations above mean) and
birth weight below the 10th percentile who required
delivery for abnormal scores in the biophysical profile.
Fetal well-being was assessed serially using all
five components of the biophysical profile and concurrent
Doppler evaluations of the umbilical artery,
middle cerebral artery, ductus venosus, inferior vena
cava, and free umbilical vein. The majority of the fetuses
did not have reactivity of the fetal heart rate.
The investigators observed significant deterioration of
the biophysical profile and Doppler studies between
the first examination and time of delivery. First, there
was a change in the Doppler variables. In 42 (95.5%)
fetuses one or more of the Doppler variables were abnormal.
The umbilical artery and ductus venosus PI
abnormalities progressed rapidly a median of 4 days
before the biophysical profile worsened. Fetal breathing
movement began to decline 2±3 days before delivery,
followed by a decrease in the amniotic fluid volume.
Loss of fetal movement and tone were observed
on the day of delivery. Additionally, in 31fetuses deterioration
in the Doppler parameters was complete
23 h before a worsening of the biophysical profile,
while in 11 fetuses deterioration of the Doppler parameters
and the biophysical profile occurred simultaneously.
The above studies indicate that Doppler velocimetry
and existing fetal monitoring techniques can be
integrated to provide greater pathophysiologic insight
into the mechanism of progressive fetal decompensation.
Such integration may provide a rational, effective
alternative to the current standards of fetal surveillance.
Summary
There is ample evidence that Doppler indices from
the fetal circulation can reliably predict adverse perinatal
outcome in an obstetric patient population with
a high prevalence of complications, such as fetal
growth restriction and hypertension. This efficacy is
not evident, however, in populations with a low prevalence
of pregnancy complications. It is also apparent
that fetal Doppler indices are capable of reflecting fetal
respiratory deficiency with varying degrees of efficiency.
The umbilical arterial Doppler indices are
more sensitive to asphyxia than to hypoxia, whereas
cerebral Doppler indices demonstrate significant sensitivity
to hypoxia. Compared to fetal heart rate monitoring
and the biophysical profile, umbilical artery