Higher order spectral analysis of heart rate variability in pregnancy and postpartum

This paper presents the study of bispectrum analysis methods of heart rate variability in normotensive pregnant and postpartum women. The self and cross spectral components are estimated from bispectrum of ECG of pregnant and postpartum women. It is observed that, very low frequency (VLF) and low frequency (LF) component coupling increases while the high frequency (HF) coupling and cross coupling between VLF-LF, VLF-HF and LF-HF decreases throughout the pregnancy. The power at very high frequencies decreases as gestation age progresses. Significant differences are found in similar and cross coupling frequency components in all three trimesters and postpartum. The results indicate that one possible discriminating dynamics for the pregnant women in all three trimesters is the absence of nonlinear interactions between the sympathetic and parasympathetic nervous systems.