Measurement characteristics of the ultrasound heart rate monitor

It was reported that the measurement error of the fetal heart rate variability (FHRV), which was obtained by a ultrasound heart rate monitor with the Doppler signal, was large even if the auto-correlation technique was used. Nevertheless, fetal heart rate monitoring by the ultrasound heart rate monitor is necessary to determine the status of the fetus because an invasive test cannot be used daily. In order to make sure the quality of the FHRV obtained from the Doppler data, we measured the fetal ECG directly from the fetal sculpture at the same time as the Doppler data. The FHRV differences of the Doppler data from the direct ECG data were found to be concentrated at 0 bpm (beats per minute), around which the pattern of distribution is practically symmetrical. Furthermore, the spectral density of the FHRV differences showed the white spectrum without dominant peaks