Monitoring the fetal heart non-invasively: a review of methods

Doppler ultrasound, ultrasound M-mode analysis, fetal electrocardiography, and fetal magnetocardiography are methods by which the fetal heart can be m onitored noninvasively. In this paper, they are evaluated and compared. Cus tomarily, it is solely the fetal heart rate, which is monitored using the D oppler ultrasound technique since it is both simple to use and cheap. Howev er, this method inherently produces an averaged heart rate and therefore ca nnot give the beat-to-beat variability. Fetal electrocardiography has simil ar advantages, but in addition offers the potential for monitoring beat-to- beat variability and performing electrocardiogram morphological analysis. I ts disadvantage is that its reliability is only 60 %, although it is the on ly technique that offers truly long-term ambulatory monitoring. Ultrasound M-mode analysis allows a estimation of atrial and ventricular coordination, as well as an estimation of PR intervals. Bradycardias, supraventricular t achycardias, extra systoles are readily diagnosed using this method althoug h timing will be inaccurate. Fetal magnetocardiograms can be detected relia bly and used for accurate beat-to-beat measurements and morphological analy sis. Consequently, they can be used for the classification of arrhythmias a nd the diagnosis of a long QT syndrome and some congenital heart diseases.