In this study we investigated fetal arrhythmias using a Superconductive Quantum Interference Device (SQUID) in a shielded environment of low magnetic noise. The subjects involved were 84 pregnant women, 1941 years old (mean=30.55, SD=7.18) with single normal uncomplicated pregnancies and gestational ages 2532 weeks and 68 pregnant women 2342 years old (mean=32.89, SD=5.28), treated with ritodrine for the risk of preterm labour; with gestational ages 2635 weeks. Fourteen fetuses were found with cardiac arrhythmia six cases with tachycardia, one with bradycardia and seven with supraventricular/ ventricular (S/V) extrasystoles. Power spectra analysis of fetal magnetocardiographic arrhythmic signals assesses the functional state of their autonomic nervous system. Thus, magnetocardiography and power spectral analysis of the arrhythmic signals inform us that there is no deviation in the physiological process of the fetal heart in cases of fetal arrhythmia.