A new method of fetal heart rate monitoring.

A new method of continuous fetal heart rate monitoring, employing for cardiotachometry the fetal electrocardiogram obtained from electrodes placed on the maternal abdomen, was evaluated over a period of 26 months at the Lying-in Division of the Boston Hospital for Women. A total of 2460 hours of intrapartum monitoring were analyzed. This "noninvasive" method of fetal ECG-based monitoring was shown to be as accurate as the direct scalp electrode method and more reliable than indirect ultrasound. Useful fetal monitoring, from very early labor up to the time of delivery, was possible in 91% of 507 patients, using maternal skin electrodes alone. Beat-to-beat variability determinations, possibly of significance in evaluating fetoplacental function in the antepartum period, were precise and without the artifactuality of ultrasonic or phonocardiographic methods.