Noninvasive fetal QRS detection using a linear combination of abdomen ECG signals

The fetal ECG can serve as a tool for fetal distress detection. However, the abdominal ECG of a pregnant woman contains mainly the maternal ECG and a relatively small amplitude fetal ECG signal, contaminated by various noises. As part of the 2013 PhysioNet/CinC Challenge, this study aimed to develop an algorithm for noninvasive fetal QRS detection. The proposed algorithm is mainly based on fetal ECG source signal enhancement using a modified linear combiner. After initial noise reduction, the maternal QRS complexes are detected. Then, fetal QRS candidates are found. For each candidate, a Gaussian-like synthetic fetal QRS signal is created. This signal is considered an observation signal for a modified linear combiner. The 4 filtered abdomen ECG signals then undergo maternal ECG cancellation and serve as reference signals in this linear combiner; hence by finding the appropriate weight coefficients, their linear combination is forced to converge to a signal that represents the fetal QRS complexes solely. The method was developed using the entire 75 1minute-long abdomen ECG training set, and its evaluation on the 100 abdomen ECG test set led to scores of 262.076 for event 4 (fetal heart rate measurement) and 27.848 for event 5 (fetal RR interval measurement).