Doppler Velocimetry in Prolonged Pregnancy
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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