Time-frequency analysis of foetal heart sound signal for the prediction of prenatal anomalies

Abstract

Motion of the foetal heart gives rise to vibrations and sounds that can be acquired through the surface of the maternal abdominal wall. The process is called foetal phonocardiography (fPCG) and its study has shown to be a very useful mechanism to evaluate the wellbeing of the unborn. These signals exhibit innate rhythms and periodicity that are more readily expressed and appreciated in terms of frequency than time units. Time-frequency distribution shows the spectral composition of signal at a particular time instant, which is also known as a spectrogram. This work investigates the analysis of foetal heart sound using time frequency distribution generated by short-time Fourier transform (STFT). An innovative method is presented for foetal heart sound acquisition, processing and coloured spectral representation, which can be used in a portable foetal home monitoring system. The outcome of the work is a numerous spectral display produced by the system for varied real and simulated foetal heart sound signals. A comparative study of normal and abnormal heart sound is presented. The spectrograms exhibit noticeable morphological differences in terms of duration and spectral composition of the sounds. The study suggests that STFT based coloured spectrograms can become an important diagnostic tool, and it is expected that the presented work will facilitate the potential use of the method in prediction of the prenatal anomalies.

Keywords:

• Foetal phonocardiography
• Spectrogram
• Prenatal anomalies
• Short-time Fourier transform