Non-invasive acquisition of fetal ECG from the maternal xyphoid process: a feasibility study in pregnant sheep and a call for open data sets

TL;DR

This study evaluated the feasibility of non-invasively acquiring fetal ECG from the maternal xyphoid process in pregnant sheep, finding current algorithms ineffective and emphasizing the need for open data sets to advance research in this area.

Contribution

The paper provides the first publicly available dataset of fetal and maternal ECG recordings from the xyphoid process in pregnant sheep, highlighting limitations of existing extraction algorithms.

Findings

Single-lead fECG extraction was unsuccessful with current algorithms.

The maternal ECG signal over the xyphoid process may not contain strong enough fetal signals.

Open data sets are essential for testing and developing better fECG extraction methods.

Abstract

Objective: The utility of fetal heart rate (FHR) monitoring can only be achieved with an acquisition sampling rate that preserves the underlying physiological information on the millisecond time scale (1000 Hz rather than 4 Hz). For such acquisition, fetal ECG (fECG) is required, rather than the ultrasound to derive FHR. We tested one recently developed algorithm, SAVER, and two widely applied algorithms to extract fECG from a single channel maternal ECG signal recorded over the xyphoid process rather than the routine abdominal signal. Approach: At 126dG, ECG was attached to near-term ewe and fetal shoulders, manubrium and xyphoid processes (n=12). FECG served as the ground-truth to which the fetal ECG signal extracted from the simultaneously-acquired maternal ECG was compared. All fetuses were in good health during surgery (pH 7.29+/-0.03, pO2 33.2+/-8.4, pCO2 56.0+/-7.8, O2Sat 78.3+/-7.6, lactate 2.8+/-0.6, BE -0.3+/-2.4). Main result: In all animals, single lead fECG extraction algorithm could not extract fECG from the maternal ECG signal over the xyphoid process with the F1 less than 50%. Significance: The applied fECG extraction algorithms might be unsuitable for the maternal ECG signal over the xyphoid process, or the latter does not contain strong enough fECG signal, although the lead is near the mother's abdomen. Fetal sheep model is widely used to mimic various fetal conditions, yet ECG recordings in a public data set form are not available to test the predictive ability of fECG and FHR. We are making this data set openly available to other researchers to foster non-invasive fECG acquisition in this animal model.