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To clarify the developmental activity of the autonomicnervous system (ANS) of the normal fetus and to compare developmental activity between normal pregnancy and the case ofintrauterine growth restriction (IUGR) using fetal magnetocardiography(FMCG).Normal pregnancy (n-35) and IUGR (n=12) cases at 28-39 and 32-37 weeks gestation, respectively were included in this study.FMCG wasrecorded using 64-channel magnetocardiography (MCG) in a magnetically shielded room.The QRS interval was derived from signal-averaged MCG;the R-R interval variability induced byan R-wave trigger was eventually adopted to calculate the coefficient of variance (CVRR) and lowfrequency/high frequency (LF/HF) ratio.The value of CVRR in the normal pregnancy groupdisplayed a slight increasing trend withgestational age (y =1.77 + 0.10x;r =0.32).However, no such trend was observed in the IUGR group.In contrast, the LF/HF ratio in the normal pregnancy group(y =0.19 + 0.04x;r =0.49) and the IUGR groups (y =0.16 + 0.04x;r =0.23) both clearlyincreased over the gestational period;the normal group showing statistical significance (one-way ANOVA: P=0.003).Analyses based on the time and frequency domains of heart rate variability using FMCG enable the evaluation of fetal ANS activity.Sympathetic nervous activity increased with gestationalage in the normal pregnancy group;however, the development of fetal ANS activity in IUGR cases might differ from that observed in the normal pregnancy group.