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Blood flow in obstetrics using Doppler ultrasound.

We describe the history of obstetric blood flow research in the human fetal circulation (1978-1982) using both continuous wave (CW) Doppler and pulsed (PW) Doppler with linear array scanning. After the initial work (mainly in Ireland, Australia, Sweden, The Netherlands and the UK) it was recognized that CW Doppler velocity waveforms were of diagnostic significance and yielded as much useful clinical information as more complex PW duplex systems. PW duplex continues to be a useful research tool where accurate Doppler sampling or mean velocity measurement is required. The measurement of fetal Doppler velocity waveforms is clinically useful in the evaluation of the 'small-for-dates' fetus and abnormalities of cardiac anatomy or rhythm. Simple CW pencil probe study of the maternal utero-placental vasculature distinguishes normal from abnormal placentation and may be useful as a screening test to predict hypertensive disease of pregnancy.