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a Chapter 25 Absent End-Diastolic Velocity in the Umbilical Artery and Its Clinical Significance 381
or the administration of magnesium sulfate to the
mother and not necessarily necrotizing enterocolitis.
Suspected necrotizing enterocolitis is a clinical diagnosis
and, in the majority of cases, the condition improves
with conservative management.
Hematologic Changes
Neonates with AREDV during fetal life are apt to develop
thrombocytopenia and anemia. They may have
a low platelet count at birth and are more likely to
become significantly thrombocytopenic during the
first week of life [36]. They are also at increased risk
of being anemic. It has also been reported [24] that
the infants with absent or reversed end-diastolic
velocity had odds ratios of 3.0 and 6.1, respectively,
for developing anemia compared to a control group
of infants. The latter were growth-restricted and their
mothers had hypertension, but they had umbilical arterial
end-diastolic forward flow. The reason for developing
anemia independent of prematurity and
other known complications remains to be determined
[24].
Baschat and colleagues [38] have also shown that
AREDV in growth-restricted fetuses is associated with
an increased risk of neonatal thrombocytopenia. In a
study comparing 67 fetuses with elevated PI (more
than two standard deviations above the mean) to 48
fetuses with AREDV, 22 of the 48 fetuses with AREDV
had thrombocytopenia (< 100,000 mm 3 ) compared to
3 of the 67 fetuses in the control group. Neonates
with AREDV had a relative risk of 10.3 or a tenfold
increase in the incidence of thrombocytopenia when
compared to the control group. In addition, neonates
with AREDV had a higher nucleated red blood cell
count than the control group. High numbers of nucleated
red blood cells in the umbilical cord have
been associated with hypoxemia during intrauterine
life and subsequent neurologic impairment.
Similarly, Axt-Fliedner and coinvestigators [39] reported
an increased number of nucleated red blood
cells in the umbilical artery at birth in growth±restricted
neonates with AREDV during fetal life when
compared to neonates with elevated Doppler studies.
Moreover, the nucleated red blood cells persisted in
the neonatal circulation for a longer period of time
in the neonates with AREDV. Nucleated red blood
cells are immature erythrocytes. They are seen in
variable numbers in the newborn circulation.
Although an increased number of nucleated red blood
cells has been attributed to increased erythropoiesis
in the fetal liver as a result of chronic hypoxemia,
these studies [38, 39] have shown that the neonates
with a higher number of nucleated red blood cells
have lower hematocrits, hemoglobin levels, and platelet
counts that the other neonates studied.
Hypoglycemia
Infants with AREDV become hypoglycemic more frequently,
and it cannot be fully attributable to preterm
gestational age or IUGR. The odds for developing hypoglycemia
is 5.0 compared to growth-compromised
fetuses without AREDV [24]. The reason for this metabolic
problem remains unclear.
Neurodevelopmental Sequelae
Any examination of the efficacy of umbilical arterial
AREDV for fetal prognostication must go beyond looking
for gross cerebral lesions (e.g., hemorrhage) and
encompass immediate and long-term neurologic performance.
Furthermore, its imperative that neurologic
outcome measures should be extended to include not
only moderate to severe neurologic deficits but also
more subtle compromises in cognitive and motor performance.
Although there it is a paucity of information
in this area, a few preliminary reports are available
concerning the neurodevelopmental significance of
AREDV. Weiss and associates [19] observed in their
case-control study (see above) an increase in abnormal
neurologic signs in the AREDV group. The pediatric
neurologic assessment was blinded to the fetal Doppler
results. The adverse signs included persistent hyperreflexia,
hypo- or hypertonia, seizures, and cerebral
palsy. Fourteen fetuses in the index group (30%) and
three fetuses in the control group (6%) demonstrated
abnormal neurologic signs at the time of discharge.
The results were statistically significant (p