Chaotic and periodic analysis of fetal magnetocardiogram recordings in growth restriction

Objective We studied how chaotic and periodic heart rate dynamics differ between normal fetuses (n = 19) and intrauterine growth restricted fetuses (n = 11) at 34 to 37 weeks of gestation. We quantified the chaotic dynamics of each heart rate time series obtained by fetal magnetocardiography (FMCG) using correlation dimension. Methods The FMCG was recorded digitally by a single-channel biornagnetometer in an electrically shielded room of low magnetic noise. The position of the fetal heart was determined using ultrasonography. Results The correlation dimension was significantly lower in IUGR than in normal fetuses (p < 0.001, t-test). The periodic dynamics were also obtained by FMCG and measured by power spectrum. The low-frequency components and therefore the periodicity of the low-frequency range were significantly higher in IUGR than in normal fetuses (1) < 0.001, t-test). Conclusions The analysis of FMCG recordings may offer important perspectives to understand significant features of the heart function of the fetuses. This technique improves the recognition of IUGR fetuses over healthv ones and may help improve perinatal morbidity and mortality. Copyright (D 2003 John Wiley Sons, Ltd.