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a Chapter 25 Absent End-Diastolic Velocity in the Umbilical Artery and Its Clinical Significance 377
timated Doppler shift because of the cosine function
of the angle in the Doppler equation (see Chap. 2). A
larger angle therefore leads to a lower frequency measurement,
which leads to disappearance of the enddiastolic
frequency even in the presence of end-diastolic
flow.
Absent End-Diastolic Velocity
and Adverse Perinatal Outcome
There is an ominous association between the AREDV
in the umbilical artery and adverse perinatal outcome
(Table 25.2). The latter includes not only morbid
states, such as fetal growth restriction, developmental
anomalies, and abnormal chromosomes, but also a
substantial increase in perinatal deaths. In addition,
there is a significant association with pregnancy complications,
such as hypertensive disease of pregnancy
and oligohydramnios.
Table 25.2. Absent and reverse end-diastolic velocity in
the umbilical artery and adverse perinatal outcome
Perinatal outcome Mean Range
Death (%) 45 17±100
Gestational age (weeks) 31.6 29±33
Birth weight (g) 1,056 910±1,481
Small-for-gestational age (%) 68 53±100
Cesarean section for fetal
73 24±100
distress (%)
Apgar score