Fetal electrocardiographic monitoring: past, present and future--a historical perspective.

The first recording of the fetal electrocardiogram was described 80 years ago. Since that time only the peak of the QRS complex has been used in fetal monitoring for the measurement of fetal heart rate. Attempts to quantify changes in the configuration and time constants have been attempted over the last 30 years but despite the data obtained from animal experiments suggesting configurational changes in relation to hypoxia, the problems of electrical noise and signal distortion have restricted the application of these observations in the detection of fetal hypoxia in the human. Recent technical developments have now enabled continuous real time monitoring of the PR interval, heart rate and ST segment, and their findings and the interrelationships between different variables suggest a new approach to precise monitoring of the fetal state.