Computerized detection of low-level fetal signals in the maternal abdominal electrocardiogram

This paper describes a method for detecting low-level fetal ECG signals in maternal abdominal ECG recordings. Detection is based on a systematic application of the principle that the fetal ECG contains proportionately greater high-frequency components than does the maternal ECG. Adaptive subtraction of the maternal high-frequency components is used to detect the fetal R-waves. The method is found to detect the fetal ECG even in many cases where the maternal and fetal R-waves coincide or occur in close proximity to each other. Recursive time-coherent averaging is then used to significantly improve the signal-to-noise ratio of the fetal ECG to the point where the fetal P and T waves may be observed.