Waveform pattern recognition--a new semiquantitative method for analysis of fetal aortic and umbilical artery blood flow velocity recorded by Doppler ultrasound.

A semiquantitative computerized waveform pattern recognition system for analysis of the fetal descending aortic and umbilical artery Doppler flow velocity waveforms is presented. Based on empirically and manually selected clinical recordings from both vessels, 11 computerized and normalized standard curves for the aorta (type curves A to K), and 10 curves for the umbilical artery (type curves a to j) were constructed. The best match between the normalized waveform and the standard curve was based on either the degree of absent diastolic flow or, in cases with positive diastolic flow, on the calculation of the least square sum of the difference. The pattern recognition was tested against conventional waveform indices and our older semiquantitative Blood Flow Class (BFC) system in 472 clinical consecutive Doppler recordings. A good correlation was found. This new relatively simple computer-based method for waveform analysis is now prospectively applied in clinical studies.