Magnetocardiography (MCG) is a technique that enables the noncontact, noninvasive measurement of electrocardiographic
phenomena, and fetal magnetocardiography (FMCG) is extremely useful for the analysis of fetal electrocardiographic
phenomena. We have used FMCG for the diagnosis and treatment of a range of fetal arrhythmias, and to perform
comparative studies of autonomic nervous system activity in fetuses with normal growth and those with fetal growth
restriction by analyzing fetal heart rate variability. In terms of fetal arrhythmias, fatal long QT syndrome was accurately
diagnosed prenatally using FMCG, and pregnancy was maintained until delivery at 37 weeks gestation. With regard to fetal
autonomic nervous system activity, there was a pronounced increase in sympathetic nervous activity among fetuses
with normal growth in the second half of pregnancy.