Fetal Doppler shift waveforms in intrauterine growth retardation: laplace transform analysis technique.

An approach to the analysis of fetal blood flow velocity/time waveforms is described using a Doppler shift flowmeter. The waveform shape is described in terms of its Laplace transform. Variations in the value of the dominant coefficient in the Laplace transform in the descending thoracic aorta appear to distinguish growth retarded from normally grown fetuses early in pregnancy. Growth retardation was defined by an index of size specifically aimed at detecting the disproportionately grown fetus. Simpler methods of waveform shape description fail to detect the growth retarded fetus early in the second trimester.