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a Chapter 23 Doppler Velocimetry in Prolonged Pregnancy 361
sistent with placental senescence even exist has been
called into question [30]. We can therefore conclude
that uterine artery and uteroplacental Doppler, when
used for the routine assessment of prolonged pregnancies,
do not predict fetuses that will subsequently
develop perinatal complications.
Conclusion
A comprehensive review of Doppler velocimetry revealed
significant variability in the design and conduct
of these studies. Areas of variability include differences
in ultrasound machines used, Doppler modality
(continuous value vs pulsed Doppler), Doppler
indices used, and definition of prolonged pregnancy
and precision of pregnancy dating. The Doppler technique
requires experience and precision that are difficult
to ensure and maintain across different trials.
The extreme variability observed is likely to overwhelm
any small or moderate correlation between
Doppler measurements and outcomes, should they
exist. The generally small size of the study samples
and the near universal lack of power analysis for
studies with negative results represent significant additional
hurdles. Properly designed and sufficiently
powered trials would therefore still be of benefit. An
interesting empirical observation was that umbilical
Doppler velocimetry appeared to better predict outcome
in prolonged pregnancy when compared with
the standard antenatal tests such as NST and fluid
volume assessment. This is certainly an observation
that merits further investigation.
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