Investigating the effect of oxygen saturation on very low frequency periodic components of the fetal heart rate during labor using matching pursuits

The objective of the present study is to examine the very low frequency periodic components of the fetal heart rate during labor in relation to the oxygen saturation of the fetal arterial blood. In order to analyze and quantify the periodic dynamics of the fetal heart rate variability in the very low frequency (VLF) range, we apply the matching pursuits (MP) method. This method has the ability to identify multiple periodicities in a highly nonstationary signal and we focus on the sinusoidal-like activities between 0.01 and 0.04 Hz. We demonstrate that the VLF activity of the fetal heart rate is increased when the oxygen saturation of the fetal arterial blood is diminished below the threshold value of 30% and the umbilical artery pH is lower than 7.15.