Computerized analysis of fetal heart rate

It was noticed that fetal heart rates of immature fetuses intermittently showed unstable sudden and brief falls below baseline fetal heart rate that occur over a few or several heartbeats. The frightening falls do not occur in mature fetuses. In nonlinear dynamics, the degree of such abrupt falls in time series is quantified as intermittency. In this project the nature and maturational changes of intermittency of the FHR in normal fetuses were investigated and the intermittency values of normal fetuses according to gestational weeks were presented. This project also presents a system capable of calculating the intermittency value and uses it to identify the fetus condition using the MATLAB 7 package. FHR data of 54 normal fetuses and 4 fetuses from pregnant women with pregnancy induced hypertension between 23 and 40 weeks of gestation were studied. The first stage in the system is to convert the cardiotocograghy tracing into digital series so that the system can analyze it. In stage two the FHR time series was analyzed using time domain analysis, power spectral density methods and multifractal analysis was performed and highlighted a veryshortterm intermittency. In stage three statistical analysis methods where used to compare between the above three methods results and to decide the best method, it was noticed that the very-short-term intermittency exhibited a strong negative linear correlation with the gestational weeks. At 27-28, 29-30, 33-34, and 37-38 gestational weeks, the very-short-term intermittency values were significantly lower than those of the previous 2 or 4 gestational weeks. The maturation of normal fetuses is related to decreasing the severity of the unstable sudden and brief falls in FHR that is measured by the veryshort- term intermittency. The very-short-term intermittency values according to the gestational weeks that were presented can be used as credible normal milestone values when estimating the degree of maturity of certain fetal heart rate. Because the very-short-term intermittency captures the degree of the unstable fall in fetal heart rate, the very-short-term intermittency may also be used in identifying sick
fetuses that are associated with hemodynamic instability and sudden bradycardia. These values were used in stage four of the system to identify sick fetuses and when analyzing fetal heart rate of 4 fetuses from pregnant women with pregnancy induced hypertension the system succeed to identify the presence of a problem in these fetuses' hearts.