Some regularity on how to locate electrodes for higher fECG SNRs

The electrocardiogram（ECG） recorded from the abdominal surface of a pregnant woman is a composite of maternal ECG, fetal ECG（f ECG） and other noises, while only the f ECG component is always needed by us. With different locations of electrode pairs on the maternal abdominal surface to measure f ECGs, the signal-to-noise ratios（SNRs） of the recorded abdominal ECGs are also correspondingly different. Some regularity on how to locate electrodes to obtain higher f ECG SNRs is needed practically. In this paper, 343 groups of abdominal ECG records were acquired from 78 pregnant women with different electrode pairs locating, and an appropriate extended research database is formed. Then the regularity on f ECG SNRs corresponding to different electrode pairs locating was studied. Based on statistical analysis, it is shown that the f ECG SNRs are significantly higher in certain locations than others. Reasonable explanation is also provided to the statistical result using the theories of the fetal cardiac electrical axis and the signal phase delay.