MAGNETOCARDIOGRAPHY IN THE SURVEILLANCE OF FETAL CARDIAC ACTIVITY

Magnetocardiography provides a new, alternative method for fetal surveillance. This method allows the registration of changes in the magnetic field produced by the fetal cardiac system. In comparison to fetal EGG, the fetal magnetocardiogram (fMCG) is not affected by intermediate tissue, in particular by the insulating effect of the vernix caseosa. Furthermore fMCG's with a good signal noise ratio can be obtained in the second trimester. A multichannel biomagnetometer allows the non-invasive measurement of the magnetic signals produced by the fetus. Examples of data and evaluation techniques are given. Signal processing software allows the identification of all fetal beats in a data set, permitting the calculation of an averaged beat and the evaluation of signal morphology and cardiac time intervals. Furthermore it is possible to produce a beat to beat time series with high temporal resolution, making the evaluation of heart rate variability with measures from the time, frequency, and phase domain accessible. Particularly: the latter are of interest in investigating changes in temporal complexity of the fetal cardiac system. Magnetocardiography thus holds the promise of improved antenatal surveillance as of the second trimester.