On the Wavelet Analysis of the Doppler Signals of Fetal Activity

The db10 wavelet was applied to the decomposition of the ultrasonic Doppler signals recorded on the abdomen of a pregnant woman. The correlation analysis of the wavelet reconstruction products enabled the detection of signals due to movements of fetal cardiac structures, fetal pseudobreathing and hiccups, maternal breathing and cardiac movements, the estimation of the corresponding rhythms, and the evaluation of the frequency ranges of the corresponding signals. Bandwidths of Doppler signals resulting from the movements of fetal cardiac structures overlap only partly with those resulting from the pseudo-breathing and the fetal hiccup. Doppler signals of maternal origin feature lower frequency contents or lower rhythms then the signals of the fetal origin and are expected not to adversely affect the estimation of the fetal rhythms. These findings may be exploited in the development of the Doppler hardware used for the collection of fetal activity signals and in the identification of signals resulting from individual fetal activities.