Prospective Clinical Testing of a "Beat-To-Beat" Extraction Method for Fetal Electrocardiography

There is a critical clinical need for fetal electrocardiography (fECG), but no methods have successfully translated to the ambulatory setting. We developed a novel fECG system combining custom hardware and null coherence-based signal processing, then evaluated its feasibility for fECG extraction in normal and at-risk pregnancies.

We applied the fECG system to 43 patients (25 normal fetuses, 18 abnormal). FECG studies were 15 min long and utilized 12-24 electrodes and 1 ground. Signal processing was done during collection with additional post-processing. Two clinician raters blinded to gestational age, indication, and each other's assessments, graded the quality of studies using a 5-point scale. The raters measured the PR, QRS, and/or QTc intervals twice where possible.

In 43 subjects, 30 had time-resolved fECG separation (70%) and the median grading (based on two raters across two sessions) was 3 or greater in 26/43 fetuses (60%) with graded studies. Sixty three percent of cases (27/43) had a measurable fetal cardiac time interval. Signal quality was reduced in participants with BMI ≥30 and during the vernix period (25-32 weeks' gestation).

Our findings demonstrate the feasibility of fECG across gestation, enabling beat-to-beat signal extraction and CTI measurement with a 63% success rate.