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Unlabelled: To investigate the relationship between imbalance of cardiac autonomic nervous system and sudden death in fetuses of rats with intrahepatic cholestasis of pregnancy (ICP), the animal model of ICP was induced by hypodermic injection of 17-alpha-ethinylestradiol and progesterone. The electrocardiograms and frequency domain analysis of heart rate variability (HRV) including low frequency (LF), high frequency (HF) and the ratio between low and high frequencies (LF/HF) of fetal rats by the 21st day of gestation were evaluated with Chart 5 software of Powerlab biologic signal extracting and analyzing system., Results: (1) The serum total bile acids (TBA) levels of pregnant rats were (78.5 +/- 4.5) micromol/L in Group ICP and (24.6 +/- 3.6) micromol/L in Group control; significant difference was noted between the two groups (P < 0.01). (2) In Group ICP, fetal rats arrhythmias appeared after (29.3 +/- 6.4) minutes' observation, and fetal rats died suddenly after (23.5 +/- 4.6) minutes' arrhythmias; However, the fetal rats in Group control all showed normal electrocardiograms over 90 minutes' continuous observation. (3) The values of LF and LF/HF of fetal rats in Group ICP within 20 minutes before fetal rats arrhythmias were significantly higher than those in Group control (LF 48.45 +/- 4.11 nu vs. 33.87 +/- 4.31 nu, and LF/HF 0.99 +/- 0.14 vs. 0.61 +/- 0.10, respectively, P < 0.01). (4) Dynamic power spectral analysis of HRV indicated that the values of LF and LF/HF of fetal rats in Group ICP increased progressively within 15 minutes before the sudden death of fetal rats. These demonstrated that autonomic imbalance in association with increased sympathetic activity has been strongly implicated in the pathophysiology of fetal arrhythmogenesis and sudden death in ICP. HRV analysis could be a useful tool for fetal surveillance, especially for ICP.

Unlabelled: This 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.