ABSTRACT
The Doppler principle involves the change in frequency of wave energy when reflected from a moving object, the frequency shift being proportional to the velocity of the reflector. Using the Doppler facility it is possible to detect blood flow by means of frequency shifts reflected by moving blood cells. Applications that have developed largely in the past decade have extended its use to virtually all medical specialties including obstetrics and gynecology, cardiology, neurology, radiology, pediatrics and surgery. In the field of perinatology, subsequent experience showed that there is a relationship between velocity waveform changes and pregnancy outcome. This aroused the interest of perinatologists in the recording of velocity waveforms from the fetal and uteroplacental arteries. The more recent advent of color and power Doppler modes has enabled blood flow signals to be recorded even from very small fetal vessels, e.g. the coronary arteries, offering information related to the function of an organ as well as its morphology. Proper application of Doppler velocimetry in perinatology includes the availability of highquality equipment in the hands of a skilful and experienced operator well aware of the various potential sources of error inherent in the method, the gathering of the primary velocity signals being of good quality and the cautious interpretation of the results.
