UNLABELLEDThis investigation was made to explore the chaotic characteristics of cardiac system and differences of autonomic nervous system development of normal pregnant rats and fetuses. The electrocardiograms, chaotic graphics and digital characteristics of heart period signal (HPS) of normal pregnant rats and fetuses by day 21st were evaluated with a computerized HPS extracting and analyzing system.

RESULTS(1) The mean values of frequency and voltage of fetal rats electrocardiograms were lower than those of pregnant rats significantly (P < 0.01). (2) Being similar to those in human, the chaotic graphics showed three-amplitudes spectral features in both normal pregnant rats and fetuses. However, the second amplitude and third amplitude were lower in fetal rats than in pregnant rats. (3) The Heart Relative Dispersion, Lyapunov Exponent and Fractional Dimension were significantly lower in fetal rats than in pregnant rats (P < 0.01). These findings demonstrated that the autonomic nervous system development of fetal rat was still immature and it exhibited lower complexity of HPS and chaotic degree than that of pregnant rat did.