Microprocessor-controlled doppler. A new fetal heart rate monitoring technique.

A new Doppler fetal heart rate (FHR) monitoring system using microprocessor-controlled ranged directional Doppler (RDD) was developed. The instrumentation was evaluated for accuracy and reproducibility of results by computer measurement and statistical analysis of the difference between FHR simultaneously obtained from Doppler and from fetal scalp electrocardiography (ECG) in 20 high-risk patients during labor. During 90% to 93.5% of the monitoring time, Doppler-derived FHR approximated ECG-FHR to within 5 beats per minute (BPM). The FHR records from this monitoring system can provide accurate and reliable external FHR information that may approximate the internal ECG-FHR record to such a degree that the practitioner is offered a reliable, noninvasive alternative to internal fetal monitoring.