Antenatal fetal magnetocardiography using SQUID´s

Since the advent of superconducting quantum interference device (SQUID) magnetometers in the late 1960\´s it has been possible to detect virtually all the electromagnetic signals produced by the human body, often with better precision than is possible by electrical measurements, and with the added advantage that no physical contact is required with the subject. However, as is obvious from the name, this is a superconducting device which requires liquid helium (and in most cases, a magnetically "clean" environment) for its operation. A significant recent advance in this connection, has been the development of robust portable SQUID biomagnetometers for operation in magnetically unshielded environments. Over the last 3 years the author has carried out a preclinical pilot study of fetal magnetocardiography (FMEG) in the maternity ward at Singleton Hospital demonstrating the viability of the technique as it routine clinical tool. So far the author has measured the FMCG from over 30 normal volunteer women in the course of uncomplicated pregnancy. The gestational age ranged from 23 weeks to a few days before delivery. The R-wave was detectable in all cases, with the signal-to-noise ratio varying between 1 and 10. The P-wave generally becomes observable after 30 weeks gestation and the T-wave after 34 weeks gestation. For each subject the following parameters were measured: fetal heart rate, duration of the QRS complex, P-R interval, and the various amplitude ratios (R/P, R/Q, R/S, R/T)