Clinical application of the Segmented-Beat Modulation Method for fetal ECG extraction

The assessment of the fetal well-being is accomplished with the monitoring of fetal cardiac activity. In presence of risk labor, direct fetal electrocardiography (fECG) can be obtained by positioning an electrode on the fetal scalp. However, its invasiveness and application limited to labor have led to the introduction of the indirect (noninvasive) fECG, obtained by applying the electrodes on the maternal abdomen. The abdominal recordings are corrupted by the maternal ECG (mECG) that often covers the fECG (the signal of interest). To extract the fECG, the mECG has to be estimated and then subtracted from the abdominal recording. To this aim, template-based techniques are often applied. However, such techniques are typically not able to reproduce physiological heart rate (HR) and morphological variability. To overcome this limit, an innovative template-based filtering technique termed the Segmented-Beat Modulation Method (SBMM) has recently been proposed. To evaluate its ability to extract the fECG, SBMM is applied here to an abdominal recording. Direct fECG was simultaneously recorded for comparison. Each RR interval of the direct fECG was correlated with the corresponding RR interval of the indirect fECG, and a statistically significant strong correlation (ρ=0.86, P<10-26) was found. Thus, the SBMM proved to be a potentially useful tool to provide a reliable fECG signal (extracted from an abdominal recording) that can be used for monitoring the fetus health conditions.