Noninvasive Fetal Electrocardiography: An Overview of the Signal Electrophysiological Meaning, Recording Procedures, and Processing Techniques

Abstract

Differences among methods rely on different techniques used to extract fECG. If pure abdominal electrode configurations are used, fECG is extracted directly from the abdominal recording using independent component analysis or template subtraction. Eventually, if mixed electrode configurations are used, the fECG can be extracted using the adaptive filtering fed with the maternal ECG recorded by the electrodes located in the woman thorax or shoulder.

T-Wave Alternans Identification in Direct Fetal Electrocardiography

“…HRAMF to identify TWA from indirect FECG, and will have to deal with high levels of noise, interferences and artifacts affecting it [11] and with the fact that TWAA is usually lead-dependent [12] (typically, indirect FECG recordings are multi-lead [13]). The main finding of this paper is that fetuses show TWA, even though in healthy conditions, when usually TWA in adults is considered an indicator of cardiac risk [5].…”

Relationship between Deceleration Areas in the Second Stage of Labor and Neonatal Acidemia

“…Although CTG is highly reliable for fetal hypoxia identification [14], its predicting value could be enhanced by combining it with fetal electrocardiography (FECG) which records the electrical activity of the fetal heart [15]. Indeed, beside FHR evaluation, FECG allows to have additional information on fetal well-being based on FECG signal morphology, such as ST-segment [16][17][18][19][20].…”

Quantification of Fetal ST-Segment Deviations

“…Despite its widespread use, visual interpretation of cardiotocographic tracings is associated with limited reliability [2]. Combination of cardiotocography with fetal electrocardiography (FECG) could be helpful to prevent fatal perinatal outcomes [3,4].…”

“…Instead, indirect FECG is acquired by positioning electrodes on the mother's abdomen during late pregnancy and labor. Direct FECG is invasive but characterized by a higher signal quality than indirect FECG, which is noninvasive but highly corrupted by noise of various kinds [3]. Independently by its acquisition modality, FECG morphology is very much related to adult electrocardiography since containing the same basic waveforms: P wave, associated to atrial depolarization; QRS complex, associated to ventricular depolarization; and T wave (and U wave, when present), associated to ventricular repolarization.…”

“…In addition to heart-rate monitoring, FECG allows clinical evaluations strictly related to its morphology [2]. Specifically, P-wave and QRS-complex duration are used to evaluate the intrauterine growth restriction [6]; widened and biphasic QRS complexes not preceded by P waves (which manifest when supraventricular extrasystoles occur) indicate cases of congenital heart diseases [7]; eventually, changes of ST segment (which connects QRS complex and T wave, and reflects the effect of fetal myocardial hypoxia) are correlated with acid-base status [3].…”