Change in complexity of fetal heart rate variability.

In a pilot study of fetal heart rate variability using magnetocardiograms it was found that substantial changes occur in complexity as the fetus matures. The self-similarity parameter increased sharply from 26 weeks to 30 weeks gestational age, while the relationship of entropy to timescale reversed during the same period. This suggests that there is distinct maturation of the autonomic nervous system during this period.