Assessment of coupling between trans-abdominally acquired fetal ECG and uterine activity by bivariate phase-rectified signal averaging analysis

Daniela Casati; Tamara Stampalija; Konstantinos Rizas; Enrico Ferrazzi; Cristina Mastroianni; Eleonora Rosti; Mariachiara Quadrifoglio; Axel Bauer

doi:10.1371/journal.pone.0094557

Assessment of coupling between trans-abdominally acquired fetal ECG and uterine activity by bivariate phase-rectified signal averaging analysis

PLoS One. 2014 Apr 23;9(4):e94557. doi: 10.1371/journal.pone.0094557. eCollection 2014.

Authors

Daniela Casati¹, Tamara Stampalija², Konstantinos Rizas³, Enrico Ferrazzi¹, Cristina Mastroianni¹, Eleonora Rosti¹, Mariachiara Quadrifoglio¹, Axel Bauer³

Affiliations

¹ Department of the Woman, Mother and Neonate, Children's Hospital Vittore Buzzi, Biomedical and Clinical Sciences School of Medicine University of Milan, Milan, Italy.
² Unit of Prenatal Diagnosis, Institute for Maternal and Child Health, IRCSS Burlo Garofolo, Trieste, Italy.
³ Department of Cardiology, Munich University Clinic, DZHK (German Centre for Cardiovascular Research), Ludwig-Maximilians University, Munich, Germany.

Abstract

Couplings between uterine contractions (UC) and fetal heart rate (fHR) provide important information on fetal condition during labor. At present, couplings between UC and fHR are assessed by visual analysis and interpretation of cardiotocography. The application of computerized approaches is restricted due to the non-stationarity of the signal, missing data and noise, typical for fHR. Herein, we propose a novel approach to assess couplings between UC and fHR, based on a signal-processing algorithm termed bivariate phase-rectified signal averaging (BPRSA).

Methods: Electrohysterogram (EHG) and fetal electrocardiogram (fECG) were recorded non-invasively by a trans-abdominal device in 73 women at term with uneventful singleton pregnancy during the first stage of labor. Coupling between UC and fHR was analyzed by BPRSA and by conventional cross power spectral density analysis (CPSD). For both methods, degree of coupling was assessed by the maximum coefficient of coherence (CPRSA and CRAW, respectively) in the UC frequency domain. Coherence values greater than 0.50 were consider significant. CPRSA and CRAW were compared by Wilcoxon test.

Results: At visual inspection BPRSA analysis identified coupled periodicities in 86.3% (63/73) of the cases. 11/73 (15%) cases were excluded from further analysis because no 30 minutes of fECG recording without signal loss was available for spectral analysis. Significant coupling was found in 90.3% (56/62) of the cases analyzed by BPRSA, and in 24.2% (15/62) of the cases analyzed by CPSD, respectively. The difference between median value of CPRSA and CRAW was highly significant (0.79 [IQR 0.69-0.90] and 0.29 [IQR 0.17-0.47], respectively; p<0.0001).

Conclusion: BPRSA is a novel computer-based approach that can be reliably applied to trans-abdominally acquired EHG-fECG. It allows the assessment of correlations between UC and fHR patterns in the majority of labors, overcoming the limitations of non-stationarity and artifacts. Compared to standard techniques of cross-correlations, such as CPSD, BPRSA is significantly superior.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Electrocardiography / methods*
Female
Heart Rate, Fetal / physiology
Humans
Labor, Obstetric / physiology
Pregnancy
Uterine Contraction / physiology

Grants and funding

The Cure Onlus Foundation provided funds for the research midwife that recruited the patients, and publication expenses. Enrico Ferrazzi is member of Cure Onlus Foundation. Monica Healthcare provided 5 ta-fECG-EHG devices and the software for the extraction of the signal. The funders had no role in study design, data analysis, decision to publish, or preparation of the manuscript.