Evolution of phase synchronization of the two frequency components of the electrohysterogram (EHG): Application to the detection of human labor

The analysis of the electrical activity of the uterus recorded externally, the electrohysterogram (EHG), may find an application in the prediction of labor. In the literature parameters that are supposed to be related to the excitability of the uterine cells have almost exclusively been used for this purpose. In the present paper we evaluate the possible use of synchronization parameters for EHG measured in several places on the uterus for this prediction. The EHG is mainly composed of two frequency components called FWL and FWH. These components may be related to the synchronization and the excitability phenomenon respectively. In order to study independently these frequency components, we extracted the corresponding ridges of the wavelet transform of the EHG using the GVF-snake method. For each frequency component we computed parameters that are related to the frequency content of the signals and parameters that consider the synchronization relationship between signals. The synchronization parameters used were the mean phase coherence and the phase entropy. The values of the different parameters were compared during pregnancy and labor by statistical analysis. The detection quality of each parameter was evaluated using ROC curves. Our results suggest that synchronization parameters could be used for the detection of labor in addition to the classical previously published parameters. Another important result of our study is that both FWH and FWL seem related to excitability but only FWL seems to be related to the synchronization of the uterus at term.