A two-channel radiotelemetry system for clinical fetal monitoring.

A radiotelemetry system for monitoring fetal heart rate and uterine contractions during labor has been developed and evaluated. The two-channel transmitter utilizes a miniature intrauterine pressure sensor which frequency modulates a subcarrier. The fetal electrocardiogram picked up by a scalp electrode is summed with the subcarrier and this direct frequency modulates the RF carrier. The transmitter has been constructed in a miniature package using conventional electronic components. A receiver system which obtains the original signals and feeds them to a conventional fetal monitor has been developed for use with this transmitter. Clinical evaluation has shown the telemetry system to provide efficacious signals.