Heart rate detection in low amplitude non-invasive fetal ECG recordings

Multi-electrode electrical measurements on the maternal abdomen may provide a valuable alternative to standard fetal monitoring. Removal of the maternal ECG from these recordings by means of subtracting a weighted linear combination of segments from preceding maternal ECG complexes, results in fetal ECG traces from which the fetal heart rate can be determined. Unfortunately, these traces often contain too much noise to determine the heart rate by R-peak detection. To overcome this limitation, an algorithm has been developed that calculates the heart rate based on cross-correlation. To validate the algorithm, noise was added to a fetal scalp ECG recording to simulate low amplitude abdominal recordings. Heart rates calculated by the algorithm were compared to the heart rates from the original scalp ECG. For simulated signals with a signal to noise ratio of 2, the coefficient of correlation was 0.99 (