Mutual information estimates of CTG synchronization

We examined the use of mutual information (MI) and the instantaneous phase of the analytic signal to address synchronization of uterine pressure (UP) and fetal heart rate (FHR). MI was used to assess the UP-FHR coupling because it is suitable for non-linear systems with non-Gaussian noise. Estimating degree of synchronicity and UP-FHR delay length is useful since they are physiological correlates to fetal hypoxia. Mutual information of the UP/FHR discriminated N and MA fetuses more often (9 of 18 epochs) and earlier (100 min) than conventional cross-correlation.