Fetal electrocardiography is among the most promising methods of modern electronic fetal monitoring. However, before they can be fully deployed in the clinical practice as a gold standard, the challenges associated with the signal quality must be solved. During the last two decades, a great amount of articles dealing with improving the quality of the fetal electrocardiogram signal acquired from the abdominal recordings have been introduced. This article aims to present an extensive literature survey of different non-adaptive signal processing methods applied for fetal electrocardiogram extraction and enhancement. It is limiting that a different non-adaptive method works well for each type of signal, but independent component analysis, principal component analysis and wavelet transforms are the most commonly published methods of signal processing and have good accuracy and speed of algorithms.

Department of Cybernetics and Biomedical Engineering Faculty of Electrical Engineering and Computer Science VSB Technical University of Ostrava 17 listopadu 15 708 33 Ostrava Czech Republic

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Martinek R., Kahankova R., Jezewski J., Jaros R., Mohylova J., Fajkus M., Nedoma J., Janku P., Nazeran H. Comparative Effectiveness of ICA and PCA in Extraction of Fetal ECG From Abdominal Signals: Toward Non-invasive Fetal Monitoring. Front. Physiol. 2018;9 doi: 10.3389/fphys.2018.00648. PubMed DOI PMC

Jagannath D., Selvakumar A.I. Issues and research on foetal electrocardiogram signal elicitation. Biomed. Signal Process. Control. 2014;10:224–244. doi: 10.1016/j.bspc.2013.11.001. DOI

Sameni R., Clifford G.D. A review of fetal ECG signal processing; issues and promising directions. Open Pac. Electrophysiol. Ther. J. 2010;3:4. doi: 10.2174/1876536X01003010004. PubMed DOI PMC

KováCs F., HorváTh C., Balogh Á.T., Hosszú G. Fetal phonocardiography—Past and future possibilities. Comput. Methods Progr. Biomed. 2011;104:19–25. doi: 10.1016/j.cmpb.2010.10.006. PubMed DOI

Adithya P.C., Sankar R., Moreno W.A., Hart S. Trends in fetal monitoring through phonocardiography: Challenges and future directions. Biomed. Signal Process. Control. 2017;33:289–305. doi: 10.1016/j.bspc.2016.11.007. DOI

Kahánková R., Jaroš R., Martinek R., Jezewski J., He W., Jezewski M., Kawala-Janik A. Non-Adaptive Methods of Fetal ECG Signal Processing. Adv. Electr. Electron. Eng. 2017;15:476–490. doi: 10.15598/aeee.v15i3.2196. DOI

Verdurmen K.M., Lempersz C., Vullings R., Schroer C., Delhaas T., van Laar J.O., Oei S.G. Normal ranges for fetal electrocardiogram values for the healthy fetus of 18–24 weeks of gestation: A prospective cohort study. BMC Preg. Childbirth. 2016;16:227. doi: 10.1186/s12884-016-1021-x. PubMed DOI PMC

Karvounis E., Tsipouras M., Papaloukas C., Tsalikakis D., Naka K., Fotiadis D. A non-invasive methodology for fetal monitoring during pregnancy. Methods Inf. Med. 2010;49:238–253. doi: 10.3414/ME09-01-0041. PubMed DOI

Jezewski J., Wrobel J., Horoba K. Comparison of Doppler ultrasound and direct electrocardiography acquisition techniques for quantification of fetal heart rate variability. IEEE Trans. Biomed. Eng. 2006;53:855–864. doi: 10.1109/TBME.2005.863945. PubMed DOI

Jezewski J., Matonia A., Kupka T., Roj D., Czabanski R. Determination of fetal heart rate from abdominal signals: Evaluation of beat-to-beat accuracy in relation to the direct fetal electrocardiogram. Biomed. Tech. 2012;57:383–394. doi: 10.1515/bmt-2011-0130. PubMed DOI

Matonia A., Kupka T., Jezewski J., Momot A., Jeżewski M., Bernys M. Comparison of instantaneous fetal heart rate extracted from abdominal and direct fetal electrocardiograms. J. Med. Inf. Technol. 2012;19:101–107.

Martinek R., Nedoma J., Fajkus M., Kahankova R., Konecny J., Janku P., Kepak S., Bilik P., Nazeran H. A phonocardiographic-based fiber-optic sensor and adaptive filtering system for noninvasive continuous fetal heart rate monitoring. Sensors. 2017;17:890. doi: 10.3390/s17040890. PubMed DOI PMC

Jaros R., Kahankova R., Martinek R., Nedoma J., Fajkus M., Slanina Z. Photonics Applications in Astronomy, Communications, Industry, and High-Energy Physics Experiments 2018. Volume 10808. International Society for Optics and Photonics; Wilga, Poland: 2018. Fetal phonocardiography signal processing from abdominal records by non-adaptive methods; p. 108083E. DOI

Skutova H., Martinek R., Jaros R., Kahankova R. A Noise Suppression Technique for Fetal Phonocardiogram Monitoring Using Adaptive Neuro-Fuzzy Interference System. IFAC Pap. Online. 2018;51:456–461. doi: 10.1016/j.ifacol.2018.07.103. DOI

Kahankova R., Martinek R., Jaros R., Nedoma J., Fajkus M., Vanus J. Least Mean Squares Adaptive Algorithms Optimization for Fetal Phonocardiogram Extraction. IFAC Pap. Online. 2018;51:60–65. doi: 10.1016/j.ifacol.2018.07.130. DOI

Varady P., Wildt L., Benyó Z., Hein A. An advanced method in fetal phonocardiography. Comput. Methods Progr. Biomed. 2003;71:283–296. doi: 10.1016/S0169-2607(02)00111-6. PubMed DOI

Yang W., Yang K., Jiang H., Wang Z., Lin Q., Jia W. Fetal heart rate monitoring system with mobile internet; Proceedings of the 2014 IEEE International Symposium on Circuits and Systems (ISCAS); Melbourne, Australia. 1–5 June 2014; pp. 443–446. DOI

Kovacs F., Horváth C., Balogh Á., Hosszú G. Extended noninvasive fetal monitoring by detailed analysis of data measured with phonocardiography. IEEE Trans. Biomed. Eng. 2011;58:64–70. doi: 10.1109/TBME.2010.2071871. PubMed DOI

Khandoker A., Ibrahim E., Oshio S., Kimura Y. Validation of beat by beat fetal heart signals acquired from four-channel fetal phonocardiogram with fetal electrocardiogram in healthy late pregnancy. Sci. Rep. 2018;8:13635. doi: 10.1038/s41598-018-31898-1. PubMed DOI PMC

Popov B., Lanzo V.F., Agarwal R. Non-Invasive Measurement of Second Heart Sound Components. 7,909,772. U.S. Patent. 2011 Mar 22;

Xie K., Zhang H., Xie S., Kun C. Method and Apparatus for Detecting Instantaneous Fetal Heart Rate of Doppler Fetal Heart Sound Based on Time-Frequency Analysis. 15/335,564. U.S. Patent. 2018 May 3;

Zhang D., Zhang Y., Ren W., Sun F., Guo Y., Sun W., Wang Y., Huang L., Cai A. Prenatal diagnosis of fetal interrupted aortic arch type A by two-dimensional echocardiography and four-dimensional echocardiography with B-flow imaging and spatiotemporal image correlation. Echocardiography. 2016;33:90–98. doi: 10.1111/echo.12996. PubMed DOI

Fetal, Echocardiography Task Force. American Institute of Ultrasound in Medicine Clinical Standards Committee AIUM practice guideline for the performance of fetal echocardiography. J. Ultrasound Med. 2011;30:127. doi: 10.7863/jum.2011.30.1.127. PubMed DOI

Persico N., Moratalla J., Lombardi C., Zidere V., Allan L., Nicolaides K. Fetal echocardiography at 11–13 weeks by transabdominal high-frequency ultrasound. Ultrasound Obstet. Gynecol. 2011;37:296–301. doi: 10.1002/uog.8934. PubMed DOI

Bowman A.W. A Practical Guide to Fetal Echocardiography: Normal and Abnormal Hearts. Radcliffe Cardiology; Buckinghamshire, UK: 2010.

Quartero H., Stinstra J., Golbach E., Meijboom E., Peters M. Clinical implications of fetal magnetocardiography. Ultrasound Obstet. Gynecol. 2002;20:142–153. doi: 10.1046/j.1469-0705.2002.00754.x. PubMed DOI

Grimm B., Haueisen J., Huotilainen M., Lange S., Leeuwen P.V., Menendez T., Peters M.J., Schleussner E., Schneider U. Recommended standards for fetal magnetocardiography. Pac. Clin. Electrophysiol. 2003;26:2121–2126. doi: 10.1046/j.1460-9592.2003.00330.x. PubMed DOI

Van Leeuwen P., Halier B., Bader W., Geissler J., Trowitzsch E., Grönemeyer D. Magnetocardiography in the diagnosis of fetal arrhythmia. BJOG. 1999;106:1200–1208. doi: 10.1111/j.1471-0528.1999.tb08149.x. PubMed DOI

Hamada H., Horigome H., Asaka M., Shigemitsu S., Mitsui T., Kubo T., Kandori A., Tsukada K. Prenatal diagnosis of long QT syndrome using fetal magnetocardiography. Prenat. Diagn. 1999;19:677–680. doi: 10.1002/(SICI)1097-0223(199907)19:7<677::AID-PD597>3.0.CO;2-Z. PubMed DOI

Kähler C., Grimm B., Schleussner E., Schneider A., Schneider U., Nowak H., Vogt L., Seewald H.J. The application of fetal magnetocardiography (FMCG) to investigate fetal arrhythmias and congenital heart defects (CHD) Prenat. Diagn. 2001;21:176–182. doi: 10.1002/1097-0223(200103)21:3<176::AID-PD22>3.0.CO;2-W. PubMed DOI

Jezewski J., Wrobel J., Matonia A., Horoba K., Martinek R., Kupka T., Jezewski M. Is abdominal fetal electrocardiography an alternative to doppler ultrasound for FHR variability evaluation? Front. Physiol. 2017;8:305. doi: 10.3389/fphys.2017.00305. PubMed DOI PMC

Jezewski J., Roj D., Wrobel J., Horoba K. A novel technique for fetal heart rate estimation from Doppler ultrasound signal. Biomed. Eng. Online. 2011;10:92. doi: 10.1186/1475-925X-10-92. PubMed DOI PMC

Wrobel J., Kupka T., Horoba K., Matonia A., Roj D., Jezewski J. Recognition of Fetal Movements–Automated Detection from Doppler Ultrasound Signals Compared to Maternal Perception. J. Med. Imaging Health Inform. 2015;5:1319–1326. doi: 10.1166/jmihi.2015.1535. DOI

Monica Healthcare. [(accessed on 17 October 2018)]; Available online: http://www.monicahealthcare.com/

Mindchild. [(accessed on 17 October 2018)]; Available online: http://www.mindchild.com/

Community Research and Development Information Service. [(accessed on 17 October 2018)]; Available online: https://cordis.europa.eu/home_en.html/

Clifford G.D., Silva I., Behar J., Moody G.B. Non-invasive fetal ECG analysis. Physiol. Meas. 2014;35:1521. doi: 10.1088/0967-3334/35/8/1521. PubMed DOI PMC

Tang H., Li T., Qiu T., Park Y. Fetal Heart Rate Monitoring from Phonocardiograph Signal Using Repetition Frequency of Heart Sounds. J. Electr. Comput. Eng. 2016;2016 doi: 10.1155/2016/2404267. DOI

Vaisman S., Salem S.Y., Holcberg G., Geva A.B. Passive fetal monitoring by adaptive wavelet denoising method. Comput. Biol. Med. 2012;42:171–179. doi: 10.1016/j.compbiomed.2011.11.005. PubMed DOI

Sänger N., Hayes-Gill B., Schiermeier S., Hatzmann W., Yuan J., Herrmann E., Louwen F., Reinhard J. Prenatal Foetal Non-invasive ECG instead of Doppler CTG—A Better Alternative? Geburtshilfe Frauenheilkund. 2012;72:630. doi: 10.1055/s-0032-1315012. PubMed DOI PMC

Cohen W.R., Hayes-Gill B. Influence of maternal body mass index on accuracy and reliability of external fetal monitoring techniques. Acta Obstet. Gynecol. Scand. 2014;93:590–595. doi: 10.1111/aogs.12387. PubMed DOI

Agostinelli A., Di Cosmo M., Sbrollini A., Burattini L., Morettini M., Di Nardo F., Fioretti S., Burattini L. Quantification of Fetal ST-Segment Deviations; Proceedings of the 2017 Computing in Cardiology (CinC); Rennes, France. 24–27 September 2017; DOI

Marcantoni I., Vagni M., Agostinelli A., Sbrollini A., Morettini M., Burattini L., Di Nardo F., Fioretti S., Burattini L. T-Wave Alternans Identification in Direct Fetal Electrocardiography; Proceedings of the 2017 Computing in Cardiology (CinC); Rennes, France. 24–27 September 2017; DOI

Joachim B., Fernando A., Sebastian Z., Julien O., Gari D. A practical guide to non-invasive foetal electrocardiogram extraction and analysis. Physiol. Meas. 37. :R1–R35. doi: 10.1088/0967-3334/37/5/R1. PubMed DOI

Agostinelli A., Grillo M., Biagini A., Giuliani C., Burattini L., Fioretti S., Di Nardo F., Giannubilo S.R., Ciavattini A., Burattini L. Noninvasive fetal electrocardiography: An overview of the signal electrophysiological meaning, recording procedures, and processing techniques. Ann. Noninvasive Electrocardiol. 2015;20:303–313. doi: 10.1111/anec.12259. PubMed DOI PMC

Neoventa: It’s All in the Beat. [(accessed on 17 October 2018)]; Available online: https://www.neoventa.com/products/stan/

Matonia A., Jezewski J., Kupka T., Horoba K., Wrobel J., Gacek A. The influence of coincidence of fetal and maternal QRS complexes on fetal heart rate reliability. Med. Biol. Eng. Comput. 2006;44:393–403. doi: 10.1007/s11517-006-0054-0. PubMed DOI

Kotas M., Jezewski J., Horoba K., Matonia A. Application of spatio-temporal filtering to fetal electrocardiogram enhancement. Comput. Methods Progr. Biomed. 2011;104:1–9. doi: 10.1016/j.cmpb.2010.07.004. PubMed DOI

Kotas M., Jezewski J., Matonia A., Kupka T. Towards noise immune detection of fetal QRS complexes. Comput. Methods Progr. Biomed. 2010;97:241–256. doi: 10.1016/j.cmpb.2009.09.005. PubMed DOI

Goldberger A.L., Amaral L.A., Glass L., Hausdorff J.M., Ivanov P.C., Mark R.G., Mietus J.E., Moody G.B., Peng C.K., Stanley H.E. Physiobank, physiotoolkit, and physionet: Components of a new research resource for complex physiologic signals. Circulation. 2000;101:e215–e220. doi: 10.1161/01.CIR.101.23.e215. PubMed DOI

Hassanpour H., Parsaei A. Fetal ECG extraction using wavelet transform; Proceedings of the 2006 International Conference on Computational Inteligence for Modelling Control and Automation and International Conference on Intelligent Agents Web Technologies and International Commerce (CIMCA’06) Vienna; Austria. 22 May 2006; p. 179. DOI

Bhoker R., Gawande J. Fetal ECG extraction using wavelet transform. ITSI Trans. Electr. Electron. Eng. 2013;1:2320–8945.

De Moor B., De Gersem P., De Schutter B., Favoreel W. DAISY: A database for identification of systems. J. A. 1997;38:4–5.

Silva I., Behar J., Sameni R., Zhu T., Oster J., Clifford G.D., Moody G.B. Noninvasive fetal ecg: The physionet/computing in cardiology challenge 2013; Proceedings of the IEEE Computing in Cardiology Conference (CinC); Zaragoza, Spain. 22–25 September 2013; pp. 149–152. PubMed PMC

Sober M.M., Marco J.G. Non-Invasive Fetal Electrocardiogram Database. PhysioNet. 1997 doi: 10.13026/C2X30H. DOI

Karvounis E., Papaloukas C., Fotiadis D., Michalis L. Fetal heart rate extraction from composite maternal ECG using complex continuous wavelet transform; Proceedings of the IEEE Computers in Cardiology; Chicago, IL, USA. 19–22 September 2004; pp. 737–740. DOI

Ravindrakumar S., Raja K.B. Fetal ECG extraction and enhancement in prenatal monitoring—Review and implementation issues; Proceedings of the IEEE Trendz in Information Sciences &Computing (TISC); Chennai, India. 17–19 December 2010; pp. 16–20. DOI

Kumar P., Sharma S.K., Prasad S. CAD for Detection of Fetal Electrocardiogram by using Wavelets and. Int. J. Appl. Eng. Res. 2016;11:2321–2326.

Van Bemmel J. Detection of weak foetal electrocardiograms by autocorrelation and crosscorrelation of envelopes. IEEE Trans. Biomed. 1968:17–23. doi: 10.1109/TBME.1968.4502528. PubMed DOI

Bergveld P., Meijer W.J. A new technique for the suppression of the MECG. IEEE Trans. Biomed. 1981:348–354. doi: 10.1109/TBME.1981.324803. PubMed DOI

Levkov C., Mihov G., Ivanov R., Daskalov I., Christov I., Dotsinsky I. Removal of power-line interference from the ECG: A review of the subtraction procedure. Biomed. Eng. Online. 2005;4:50. doi: 10.1186/1475-925X-4-50. PubMed DOI PMC

Hon E., Lee S. Averaging techniques in fetal electrocardiography. Med. Electron. Biol. Eng. 1964;2:71–76. doi: 10.1007/BF02474362. PubMed DOI

Varady P. Wavelet-based adaptive denoising of phonocardiographic records; Proceedings of the 23rd Annual International Conference of the IEEE Engineering in Medicine and Biology Society; Istanbul, Turkey. 25–28 October 2001; pp. 1846–1849. DOI

Alcaraz R., Rieta J. Adaptive singular value QRST cancellation for the analysis of short single lead atrial fibrillation electrocardiograms; Proceedings of the IEEE Computers in Cardiology; Durham, NC, USA. 30 September–3 October 2007; pp. 513–516. DOI

Chmelka L., Kozumplik J. Wavelet-basedwiener filter for electrocardiogram signal denoising; Proceedings of the IEEE Computers in Cardiology; Lyon, France. 25–28 September 2005; pp. 771–774. DOI

Sun Y., Chan K.L., Krishnan S.M. ECG signal conditioning by morphological filtering. Comput. Biol. Med. 2002;32:465–479. doi: 10.1016/S0010-4825(02)00034-3. PubMed DOI

Moody G.B., Mark R.G. The impact of the MIT-BIH arrhythmia database. IEEE Eng. Med. Biol. Mag. 2001;20:45–50. doi: 10.1109/51.932724. PubMed DOI

Su L., Wu H.T. Extract fetal ECG from single-lead abdominal ECG by de-shape short time Fourier transform and nonlocal median. Front. Appl. Math. Stat. 2017;3:2. doi: 10.3389/fams.2017.00002. DOI

Andreotti F., Behar J., Zaunseder S., Oster J., Clifford G.D. An open-source framework for stress-testing non-invasive foetal ECG extraction algorithms. Physiol. Meas. 2016;37:627–648. doi: 10.1088/0967-3334/37/5/627. PubMed DOI

He P.J., Chen X.M., Liang Y., Zeng H.Z. Extraction for fetal ECG using single channel blind source separation algorithm based on multi-algorithm fusion; Proceedings of the MATEC Web of Conferences, EDP Sciences; Hong Kong, China. 26–27 April 2016;

Agostinelli A., Sbrollini A., Burattini L., Fioretti S., Di Nardo F., Burattini L. Noninvasive fetal electrocardiography part II: Segmented-Beat Modulation Method for signal denoising. Open Biomed. Eng. J. 2017;11:25–35. doi: 10.2174/1874120701711010025. PubMed DOI PMC

Lee K.J., Lee B. Sequential total variation denoising for the extraction of fetal ECG from single-channel maternal abdominal ECG. Sensors. 2016;16:1020. doi: 10.3390/s16071020. PubMed DOI PMC

Warbhe A.D., Dharaskar R.V., Kalambhe B. A single channel phonocardiograph processing using EMD, SVD, and EFICA; Proceedings of the 2010 3rd International Conference on Emerging Trends in Engineering and Technology (ICETET); Goa, India. 19–21 November 2010; pp. 578–581. DOI

Ahuja E., Shaikh F. A Novel Approach to FEG Extraction Based on Fast ICA. Int. Res. J. Eng. Technol. 2016;3:2450–2453.

Pani D., Argiolas S., Raffo L. A dsp algorithm and system for real-time fetal ecg extraction; Proceedings of the IEEE Computers in Cardiology; Bologna, Italy. 14–17 September 2008; pp. 1065–1068. DOI

BIOMED . Biomed Database. Katholieke Universiteit Leuven; Leuven, Belgium: 2005.

De Lathauwer L. Private Communication. Katholieke Universiteit Leuven; Leuven, Belgium: 2010.

Ananthanag K., Sahambi J. Investigation of blind source separation methods for extraction of fetal ECG; Proceedings of the IEEE Canadian Conference on Electrical and Computer Engineering (CCECE); Montreal, QC, Canada. 4–7 May 2003; pp. 2021–2024. DOI

Marossero D.E., Erdogmus D., Euliano N., Principe J.C., Hild K. Independent components analysis for fetal electrocardiogram extraction: A case for the data efficient mermaid algorithm; Proceedings of the IEEE 13th Workshop on Neural Networks for Signal Processing (NNSP’03); Toulouse, France. 17–19 September 2003; pp. 399–408. DOI

Camargo-Olivares J.L., Martín-Clemente R., Hornillo-Mellado S., Elena M., Román I. The maternal abdominal ECG as input to MICA in the fetal ECG extraction problem. IEEE Signal Process. Lett. 2011;18:161–164. doi: 10.1109/LSP.2011.2104415. DOI

Sevim Y., Atasoy A. Performance evaluation of nonparametric ICA algorithm for fetal ECG extraction. Turk. J. Electr. Eng. Comput. Sci. 2011;19:657–666.

Ye Y., Zhang Z.L., Zeng J., Peng L. A fast and adaptive ICA algorithm with its application to fetal electrocardiogram extraction. Appl. Math. Comput. 2008;205:799–806. doi: 10.1016/j.amc.2008.05.117. DOI

Cichocki A., Amari S.I., Siwek K., Tanaka T., Phan A.H., Zdunek R., Cruces S., Georgiev P., Washizawa Y., Leonowicz Z., et al. ICALAB Toolboxes. [(accessed on 17 October 2018)]; Available online: http://www.bsp.brain.riken.jp/ICALAB.

Leach S. Singular Value Decomposition—A Primer. [(accessed on 17 October 2018)]; Available online: http://www.citeulike.org/group/474/article/493979.

De Lathauwer L., De Moor B., Vandewalle J. SVD-based methodologies for fetal electrocardiogram extraction; Proceedings of the IEEE International Conference on Acoustics, Speech, and Signal Processing (ICASSP’00); Istanbul, Turkey. 5–9 June 2000; pp. 3771–3774. DOI

Romero I. PCA-based noise reduction in ambulatory ECGs; Proceedings of the IEEE Computing in Cardiology; Belfast, UK. 26–29 September 2010; pp. 677–680.

Bacharakis E., Nandi A.K., Zarzoso V. Foetal ECG extraction using blind source separation methods; Proceedings of the 8th IEEE European Signal Processing Conference (EUSIPCO); Trieste, Italy. 10–13 September 1996; pp. 1–4.

Kharabian S., Shamsollahi M.B., Sameni R. Fetal R-wave detection from multichannel abdominal ECG recordings in low SNR; Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC); Hilton Minneapolis, MN, USA. 3–6 September 2009; Sep 20, pp. 344–347. PubMed DOI

Martens S.M., Rabotti C., Mischi M., Sluijter R.J. A robust fetal ECG detection method for abdominal recordings. Physiol. Meas. 2007;28:373–388. doi: 10.1088/0967-3334/28/4/004. PubMed DOI

Barros A.K., Cichocki A. Extraction of specific signals with temporal structure. Neural Comput. 2001;13:1995–2003. doi: 10.1162/089976601750399272. PubMed DOI

Zhang Z.L., Ye Y. Extended Barros’s extraction algorithm with its application in fetal ECG extraction; Proceedings of the IEEE International Conference on Neural Networks and Brain (ICNN&B’05); Beijing, China. 13–15 October 2005; pp. 1077–1080. DOI

Zhang Z.L., Yi Z. Extraction of a source signal whose kurtosis value lies in a specific range. Neurocomputing. 2006;69:900–904. doi: 10.1016/j.neucom.2005.07.002. DOI

Jafari F., Tinati M.A., Mozaffari B. A new fetal ECG extraction method using its skewness value which lies in specific range; Proceedings of the 18th Iranian Conference on Electrical Engineering (ICEE); Isfahan, Iran. 11–13 May 2010; pp. 30–34. DOI

Varanini M., Tartarisco G., Balocchi R., Macerata A., Pioggia G., Billeci L. A new method for QRS complex detection in multichannel ECG: Application to self-monitoring of fetal health. Comput. Biol. Med. 2017;85:125–134. doi: 10.1016/j.compbiomed.2016.04.008. PubMed DOI

Redif S. Fetal electrocardiogram estimation using polynomial eigenvalue decomposition. Turk. J. Electr. Eng. Comput. Sci. 2016;24:2483–2497. doi: 10.3906/elk-1401-19. DOI

Tan B., Peng Q., Lin J., Li M. A novel method for estimating source number of fetal ECG; Proceedings of the 2015 International Conference on Wireless Communications & Signal Processing (WCSP); Nanjing, China. 15–17 October 2015; pp. 1–6. DOI

Da Poian G., Bernardini R., Rinaldo R. Separation and analysis of fetal-ecg signals from compressed sensed abdominal ecg recordings. IEEE Trans. Biomed. Eng. 2016;63:1269–1279. doi: 10.1109/TBME.2015.2493726. PubMed DOI

Matonia A., Jezewski J., Horoba K., Gacek A., Labaj P. The maternal ECG suppression algorithm for efficient extraction of the fetal ECG from abdominal signal; Proceedings of the 28th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBS’06); New York, NY, USA. 30 August–3 September 2006; pp. 3106–3109. PubMed DOI

Akbari H., Shamsollahi M.B., Phlypo R. Fetal ECG extraction using πTucker decomposition; Proceedings of the International Conference on Systems, Signals and Image Processing (IWSSIP); London, UK. 10–12 September 2015; pp. 174–178. DOI

Gupta P., Sharma K., Joshi S. Fetal heart rate extraction from abdominal electrocardiograms through multivariate empirical mode decomposition. Comput. Biol. Med. 2016;68:121–136. doi: 10.1016/j.compbiomed.2015.11.007. PubMed DOI

Radek Martinek. [(accessed on 17 October 2018)]; Available online: www.sites.google.com/site/martinekradek/scientific-activity.

Liu G., Luan Y. An adaptive integrated algorithm for noninvasive fetal ECG separation and noise reduction based on ICA-EEMD-WS. Med. Biol. Eng. Comput. 2015;53:1113–1127. doi: 10.1007/s11517-015-1389-1. PubMed DOI

Behar J., Andreotti F., Zaunseder S., Li Q., Oster J., Clifford G.D. An ECG simulator for generating maternal-foetal activity mixtures on abdominal ECG recordings. Physiol. Meas. 2014;35:1537. doi: 10.1088/0967-3334/35/8/1537. PubMed DOI

Gupta A., Srivastava M., Khandelwal V., Gupta A. A Novel approach to fetal ECG extraction and enhancement using blind source separation (BSS-ICA) and adaptive fetal ECG enhancer (AFE); Proceedings of the IEEE 6th International Conference on Information, Communications & Signal Processing; Singapore. 10–13 December 2007; pp. 1–4. DOI

Kotas M. Combined application of independent component analysis and projective filtering to fetal ECG extraction. Biocybern. Biomed. Eng. 2008;28:75–93.

Bergveld P., Kolling A.J., Peuscher J.H. Real-time fetal ECG recording. IEEE Trans. Biomed. Eng. 1986:505–509. doi: 10.1109/TBME.1986.325737. PubMed DOI

Sameni R., Jutten C., Shamsollahi M.B. Multichannel electrocardiogram decomposition using periodic component analysis. IEEE Trans. Biomed. Eng. 2008;55:1935–1940. doi: 10.1109/TBME.2008.919714. PubMed DOI

Martin-Clemente R., Camargo-Olivares J.L., Hornillo-Mellado S., Elena M., Roman I. Fast technique for noninvasive fetal ECG extraction. IEEE Trans. Biomed. Eng. 2011;58:227–230. doi: 10.1109/TBME.2010.2059703. PubMed DOI

Gao P., Chang E.C., Wyse L. Blind separation of fetal ECG from single mixture using SVD and ICA; Proceedings of the Joint Conference of the Fourth International Conference on Information, Communications and Signal Processing and Fourth Pacific Rim Conference on Multimedia; Singapore. 15–18 December 2003; pp. 1418–1422. DOI

Ma M., Yang Y.L., Lei S.Y. Blind extraction of fECG combining periodicity and kurtosis; Proceedings of the 3rd International Conference on Bioinformatics and Biomedical Engineering (ICBBE); Beijing, China. 11–13 June 2009; pp. 1–4. DOI

Ayat M., Assaleh K., Al-Nashash H. Fetal ECG extraction from a single abdominal ECG signal using SVD and polynomial classifiers; Proceedings of the IEEE Workshop on Machine Learning for Signal Processing (MLSP); Cancun, Mexico. 16–19 October 2008; pp. 250–254. DOI

Ayat M., Assaleh K., Al-Nashash H. Extracting fetal ECG from a single maternal abdominal record; Proceedings of the IEEE 8th GCC Conference and Exhibition (GCCCE); Muscat, Oman. 1–4 February 2015; pp. 1–4. DOI

Baska-Vincze B., Baska F., Szenci O. Fetal heart rate and fetal heart rate variability in Lipizzaner broodmares. Acta Vet. Hung. 2015;63:89–99. doi: 10.1556/AVet.2015.007. PubMed DOI

Maheshwari P., Alphonse J., Henry A., Wang J., Redmond S., Welsh A. Beat-to-beat variability of fetal myocardial performance index. Ultrasound Obstet. Gynecol. 2017;50:215–220. doi: 10.1002/uog.16012. PubMed DOI

Fruhman G., Gavard J.A., McCormick K., Wilson-Griffin J., Amon E., Gross G.A. Standard External Doppler Fetal Heart Tracings (efhr) Versus External Fetal Ecg (fecg) in Premature Gestations [17q] Obstet. Gynecol. 2016;127:143S. doi: 10.1097/01.AOG.0000483575.77421.68. PubMed DOI PMC

Becker J.H., Krikhaar A., Schuit E., Mårtendal A., Maršál K., Kwee A., Visser G.H., Amer-Wåhlin I. The added predictive value of biphasic events in ST analysis of the fetal electrocardiogram for intrapartum fetal monitoring. Acta Obstet. Gynecol. Scand. 2015;94:175–182. doi: 10.1111/aogs.12548. PubMed DOI

Sacco A., Muglu J., Navaratnarajah R., Hogg M. ST analysis for intrapartum fetal monitoring. Obstet. Gynaecol. 2015;17:5–12. doi: 10.1111/tog.12154. DOI

Rosen K. Fetal Scalp Electrode. 10/380,556. U.S. Patent. 2004 Jan 22;

Fuchs T., Grobelak K., Pomorski M., Zimmer M. Fetal Heart Rate Monitoring Using Maternal Abdominal Surface Electrodes in Third Trimester: Can We Obtain Additional Information Other than CTG Trace? Adv. Clin. Exp. Med. 2016;25:309–316. doi: 10.17219/acem/60842. PubMed DOI

A novel algorithm based on ensemble empirical mode decomposition for non-invasive fetal ECG extraction

Advanced Bioelectrical Signal Processing Methods: Past, Present and Future Approach-Part I: Cardiac Signals

New Method for Beat-to-Beat Fetal Heart Rate Measurement Using Doppler Ultrasound Signal

Fetal electrocardiograms, direct and abdominal with reference heartbeat annotations