Abstract

Fetal monitors for automatically and continuously monitoring the well-being of a fetus. The preferably ambulatory monitors include one or more fetal cardiac sensors for detecting the fetal heart rate. The sensors can be acoustic, electrocardiographic or bioimpedence types. Interference sensors are included for selectively sensing the principle interference components contained in the fetal cardiac sensor signals. The preferred microprocessor based signal processing system converts the sensor signals into digital format and transforms the signals from time domain into frequency domain and back into time domain after appropriate processing. Adaptive cancellation of interfering signals and other signal enhancing operations are disclosed. Analytical subsystems continuously analyze the fetal heart rate information and information from a fetal movement sensor to perform a fetal non-stress test. Subsystems for other analytical tests are also disclosed. Alarms warn the mother when fetal behavior is outside of preprogrammed acceptable limits of such analytical tests so that remedial action may be initiated. The monitoring system also preferably includes a sensor belt for properly and conveniently wearing the sensors and a control unit containing the signal processing and related components.