However, developing mechanism of FHR changes was almost unknown, while subjective Fetal Heart Rate (FHR) patterns were discussed in clinical studies, then discrepancies between FHR deceleration and fetal outcome were discussed, and CTG was difficult to clarify fetal complications, though perinatal outcome was reported improved by fetal monitoring . Fetal scalp lead ECG was used to record FHR, then changed to fetal heart sound by Hammaher and Maeda, then further changed to ultrasonic Doppler fetal heart beat signals treated by autocorrelation heart rate meter, because the Doppler fetal heart signal was clearly detected even in the labor and autocorrelation heart rate meter recorded FHR as clearly as fetal scalp ECG. Ominous hypoxic signs were almost unknown, benign physiologic sinusoidal FHR was not separated from ominous pathologic sinusoidal one, fetal non-reactive state was diagnosed by maternal perception of fetal movement, and fetal hiccupping movement was unable to record on the CTG. Discrepancy was discussed between late decelerations and fetal outcome.
The author intended to compare the FHR to objective fetal movement record on the recording chart, and studied ultrasonic Doppler signals of fetal movement and fetal heart beat, then achieved to objectively differentiate their Doppler signals by their frequencies. Maternal motions developed large Doppler signals; however they were differentiated by their very low frequency.