Dynamic of couplings between fetal heart rate and uterine contractions

The purpose of this study is to highlight the dynamic relationship between the cardiotocographic signals: intrapartum fetal heart rate and uterine pressure, for normal and hypoxic fetuses. The database used in our study contains 531 normal or abnormal recordings (abnormal recordings are considered those with pH value under 7.15). We have used the partial directed coherence (PDC) method to obtain the correlation parameter values and to investigate the coupling between fetal heart rate and uterine contractions for normal and abnormal recordings. To determine the difference between the coupling levels we divide the database into two groups: 100 normal recordings as a control group, and the remaining 431 normal or abnormal recordings as a test group, in order to apply the t-test with p<0.05 for the correlation parameters obtained. We computed the standard deviation and Shannon entropy of the correlation parameters obtained with the PDC method to highlight the complexity of the correlation.