Measurement accuracy of ultrasound heart rate monitor [versus ECG]

In order to ensure the accuracy of the fetal heart rate (FHR) obtained from the ultrasound Doppler data, the authors measure the fetal electrocardiogram (ECG) directly and obtain the Doppler data simultaneously. The FHR differences of the Doppler data from the direct ECG data are considerably small, concentrated at 0 bpm (beats per minute), and are practically symmetrical. The distribution was found to be close to the Student's t distribution. Furthermore, the 1/f fluctuation is observed both with the ultrasound Doppler FHR and with the direct ECG FHR. Thus, it is confirmed that the FHR observation and observation of the 1/f fluctuation using the ultrasound Doppler FHR are as useful as the direct ECG.