Correlations of fetal cardiac sympathetic activity with maternal body mass index

We tested the hypothesis that maternal body mass index (BMI) determines fetal cardiac sympathetic activity. Heart rate variability (HRV) parameters of fetal are measured for obese & non-obese mother prior to delivery with Doppler ultrasound method. We studied 64 maternal abdominal Doppler ultrasound signals. From these, we identify 41 subjects of whose body mass index (BMI) ranging from 20 to 37. The R-R interval variability which shows the variation between consecutive heart beats, change over time was eventually adopted to calculate for time-domain, frequency domain and non linear analysis. Based on frequency analysis, the ranges of the LF and HF domains were defined as 0.04-0.15 and 0.15-0.4 Hz, respectively. We defined low frequency/high frequency (LF/HF) ratio as a index of sympathetic activity. The value of LF/HF ratio [Nonparametric Fast Fourier Transform (FFT) Based method] in normal pregnancy group displayed clearly decreasing trend with body mass index (BMI) y = - 0.013x + 0.965; R² = 0.040 (one-way ANOVA: P <; 0.0001). The value of LF/HF ratio [Parametric Autoregressive (AR) Based] in normal pregnancy group displayed clearly decreasing trend with body mass index (BMI) y = - 0.011x + 0.8555; R² = 0.051 (one-way ANOVA: P <; 0.0001). In consultation with gynecologists and child specialist it has been verified that the new born babies have more neurological problems following deliveries from obese mothers compared with deliveries from non-obese mothers.