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Chapter 26
Doppler Velocimetry for Fetal Surveillance:
Randomized Clinical Trials and Implications
for Practice
Dev Maulik, Reinaldo Figueroa
The cumulative clinical evidence indicates that Doppler
velocimetry of the fetal circulation is an effective
tool for recognizing fetal compromise in high-risk
pregnancies. It has prompted many to propose its introduction
as a standard for fetal surveillance. However,
such enthusiasm must be tempered by a critical
appraisal of the efficacy and benefits of the technique.
Introduction of a new diagnostic test involves
the sequential and often parallel research process of
generating evidence that transforms the promises of a
new technique into an effective diagnostic tool that
delivers measurable benefits (Fig. 26.1).
The process begins with recognition of the potential
of a new technology to measure a clinically relevant
variable, followed by demonstration of the feasibility
of using the technology. This phase is followed
by the collection and analysis of normative data on
the test, which includes determining the physiologic
variations in the test value and establishing its range
under normal circumstances. Any possible association
between the test and the disease process is then
investigated. The next step involves studying the diagnostic
efficacy of the test for discriminating between
the diseased and nondiseased states. Often a
test is introduced into clinical practice at this stage
based on the affirmative demonstration of its diagnostic
efficacy. However, the diagnostic efficacy may
not translate into any tangible benefit for the patient.
Indeed, a new test may not be more beneficial than
the existing tests; its introduction may unnecessarily
increase the cost of care, and it may even be detrimental.
It is imperative therefore to demonstrate
without bias that utilization of the test improves clinical
outcome, which can be accomplished by randomized
clinical trials. It is regrettable that most modalities
of fetal surveillance in current practice are not
based on such evidence.
It is encouraging to note that with regard to Doppler
velocimetry for fetal surveillance, 21 clinical trials [1±
21] have been fully reported from 1987 until 2003 in
the peer-reviewed literature. In addition, during that
period limited information was available on five published
or presented randomized trials comprising two
review articles [2, 22] and three abstracts [23±25]. All
the studies evaluated umbilical arterial velocimetry; a
few also used uterine arterial velocimetry. There have
been ongoing meta-analyses of these studies as they
became available first in the Oxford Perinatal Database
and subsequently in the Cochrane Center electronic
publications. The initial comprehensive meta-analysis
by Alfirevic and Neilson [26] was published in 1995.
Since that initial meta-analysis the data have been reanalyzed
various times evaluating high- and low-risk
pregnancies separately, or evaluating high-risk pregnancies
with well-defined candidates (IUGR, hypertension)
[27±31]. The original studies are comprehensively
reviewed here, and the implications of their findings
on the clinical practice of high-risk obstetrics are
discussed. The review process included both the traditional
and meta-analytic approaches.
Doppler Randomized Trials:
A Summary
Fig. 26.1. Steps for developing a new diagnostic test, from
the feasibility study to the introduction to clinical practice
The essential features of the 21 published randomized
trials are listed in Table 26.1 and are summarized below
both individually and as a group. The sequence
is according to the chronology of their publication.
Trudinger and associates [1] were the first to report
a randomized trial on umbilical arterial Doppler
velocimetry. The aim was to assess the impact of