Power spectral analysis of plethysmographic pulse waveform in pregnant women

Abstract

To investigate the effect of pregnancy on the pulse wave of the mother. Pulse waveforms recorded via a pulse oximeter from the left index finger of non-pregnant women and pregnant women in the three trimesters of pregnancy were Fourier transformed into power spectra. Spectral indices of the power spectra of pulse waveform were obtained and compared among non-pregnant women and pregnant women in the three trimesters of pregnancy. The power of harmonics of pulse wave decayed exponentially with respect to the order of harmonics. The exponent and initial value of exponential decay for the power of harmonics and the power of the 2nd harmonic were increased, whereas the total power of pulse and the powers of higher order harmonics were decreased during pregnancy. The power of harmonics of pulse wave can be described by an exponential decay function with respect to the order of harmonics in both non-pregnant and pregnant women. The effects of pregnancy on the pulse wave are the reduction in the total power of pulse and the power of higher order harmonics, and the increase in the power of lower order harmonics in the power spectrum of pulse wave. This effect of pregnancy on the pulse wave might be caused by the decrease in vascular resistance during pregnancy, the increase in workload on the heart due to increased demand of the growing fetus, and the aortocaval compression caused by the progressively enlarged gravid uterus and fetus.