{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,5,15]],"date-time":"2026-05-15T05:41:22Z","timestamp":1778823682926,"version":"3.51.4"},"reference-count":41,"publisher":"MDPI AG","issue":"8","license":[{"start":{"date-parts":[[2020,7,22]],"date-time":"2020-07-22T00:00:00Z","timestamp":1595376000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Entropy"],"abstract":"<jats:p>Phase Entropy (PhEn) was recently introduced for evaluating the nonlinear features of physiological time series. PhEn has been demonstrated to be a robust approach in comparison to other entropy-based methods to achieve this goal. In this context, the present study aimed to analyze the nonlinear features of raw electrohysterogram (EHG) time series collected from women at the third trimester of pregnancy (TT) and later during term active parturition (P) by PhEn. We collected 10-min longitudinal transabdominal recordings of 24 low-risk pregnant women at TT (from 35 to 38 weeks of pregnancy) and P (&gt;39 weeks of pregnancy). We computed the second-order difference plots (SODPs) for the TT and P stages, and we evaluated the PhEn by modifying the k value, a coarse-graining parameter. Our results pointed out that PhEn in TT is characterized by a higher likelihood of manifesting nonlinear dynamics compared to the P condition. However, both conditions maintain percentages of nonlinear series higher than 66%. We conclude that the nonlinear features appear to be retained for both stages of pregnancy despite the uterine and cervical reorganization process that occurs in the transition from the third trimester to parturition.<\/jats:p>","DOI":"10.3390\/e22080798","type":"journal-article","created":{"date-parts":[[2020,7,22]],"date-time":"2020-07-22T03:23:16Z","timestamp":1595388196000},"page":"798","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":12,"title":["Phase Entropy Analysis of Electrohysterographic Data at the Third Trimester of Human Pregnancy and Active Parturition"],"prefix":"10.3390","volume":"22","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-5361-5007","authenticated-orcid":false,"given":"Jos\u00e9 Javier","family":"Reyes-Lagos","sequence":"first","affiliation":[{"name":"Faculty of Medicine, Autonomous University of the State of Mexico (UAEMex), Toluca 50180, Mexico"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Adriana Cristina","family":"Pliego-Carrillo","sequence":"additional","affiliation":[{"name":"Faculty of Medicine, Autonomous University of the State of Mexico (UAEMex), Toluca 50180, Mexico"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Claudia Ivette","family":"Ledesma-Ram\u00edrez","sequence":"additional","affiliation":[{"name":"Faculty of Medicine, Autonomous University of the State of Mexico (UAEMex), Toluca 50180, Mexico"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Miguel \u00c1ngel","family":"Pe\u00f1a-Castillo","sequence":"additional","affiliation":[{"name":"Basic Sciences and Engineering Division (CBI), Campus Iztapalapa, Metropolitan Autonomous University (UAM), Mexico City 09340, Mexico"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3236-2121","authenticated-orcid":false,"given":"Mar\u00eda Teresa","family":"Garc\u00eda-Gonz\u00e1lez","sequence":"additional","affiliation":[{"name":"Basic Sciences and Engineering Division (CBI), Campus Iztapalapa, Metropolitan Autonomous University (UAM), Mexico City 09340, Mexico"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3458-197X","authenticated-orcid":false,"given":"Gustavo","family":"Pacheco-L\u00f3pez","sequence":"additional","affiliation":[{"name":"Biological and Health Sciences Division (CBS), Campus Lerma, Metropolitan Autonomous University (UAM), Lerma 52005, Mexico"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Juan Carlos","family":"Echeverr\u00eda","sequence":"additional","affiliation":[{"name":"Basic Sciences and Engineering Division (CBI), Campus Iztapalapa, Metropolitan Autonomous University (UAM), Mexico City 09340, Mexico"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2020,7,22]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"21","DOI":"10.1515\/slgr-2015-0039","article-title":"Entropy-based algorithms in the analysis of biomedical signals","volume":"43","author":"Borowska","year":"2015","journal-title":"Stud. Logic Gramm. Rhetor."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"8","DOI":"10.1080\/jmf.14.1.8.21","article-title":"Analysis of uterine contractions: A dynamical approach","volume":"14","author":"Nagarajan","year":"2003","journal-title":"J. Matern. Neonatal Med."},{"key":"ref_3","first-page":"46","article-title":"Usefulness of the electrohysterography in the clinical field as a technique for uterine monitoring: A literature review","volume":"87","year":"2019","journal-title":"Ginecol. Obstet. Mex."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"27","DOI":"10.1016\/j.medengphy.2018.04.002","article-title":"Electrohysterographic characterization of the uterine myoelectrical response to labor induction drugs","volume":"56","author":"Perales","year":"2018","journal-title":"Med. Eng. Phys."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"02TR01","DOI":"10.1088\/1361-6579\/aaad56","article-title":"Electrohysterography in the diagnosis of preterm birth: A review","volume":"39","author":"Perales","year":"2018","journal-title":"Physiol. Meas."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"1124","DOI":"10.1177\/1933719118768700","article-title":"Feasibility of transabdominal electrohysterography for analysis of uterine activity in nonpregnant women","volume":"25","author":"Sammali","year":"2018","journal-title":"Reprod. Sci."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"875","DOI":"10.1109\/TBME.2017.2723933","article-title":"Dedicated Entropy Measures for Early Assessment of Pregnancy Progression from Single-Channel Electrohysterography","volume":"65","author":"Mischi","year":"2018","journal-title":"IEEE Trans. Biomed. Eng."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"1636","DOI":"10.1016\/0002-9378(93)90456-S","article-title":"Uterine electromyography: A critical review","volume":"169","author":"Devedeux","year":"1993","journal-title":"Am. J. Obstet. Gynecol."},{"key":"ref_9","doi-asserted-by":"crossref","unstructured":"Oczeretko, E., Kitlas, A., Swiatecka, J., Borowska, M., and Laudanski, T. (2005). Nonlinear Dynamics in Uterine Contractions Analysis. Fractals in Biology and Medicine, Birkh\u00e4user-Verlag.","DOI":"10.1007\/3-7643-7412-8_21"},{"key":"ref_10","doi-asserted-by":"crossref","unstructured":"Garcia-Gonzalez, M.T., Charleston-Villalobos, S., Gonzalez-Camarena, R., Garcia-Ruiz, A.C., and Aljama-Corrales, T. (2019, January 23\u201327). Characterization of EHG Contractions at Pregnancy and Term Labor by Multiscale Entropy Analysis. Proceedings of the 2019 41st Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC), Berlin, Germany.","DOI":"10.1109\/EMBC.2019.8856969"},{"key":"ref_11","doi-asserted-by":"crossref","unstructured":"Moslem, B., Khalil, M., Marque, C., and Diab, M.O. (September, January 31). Complexity analysis of the uterine electromyography. Proceedings of the 2010 Annual International Conference of the IEEE Engineering in Medicine and Biology, Buenos Aires, Argentina.","DOI":"10.1109\/IEMBS.2010.5626065"},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"13","DOI":"10.1016\/j.compbiomed.2015.10.005","article-title":"A non-linear parameterization of multivariate electrohysterographical signals","volume":"67","author":"Radomski","year":"2015","journal-title":"Comput. Biol. Med."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"105006","DOI":"10.1088\/1361-6579\/ab499e","article-title":"Phase entropy: A new complexity measure for heart rate variability","volume":"40","author":"Rohila","year":"2019","journal-title":"Physiol. Meas."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"75","DOI":"10.3233\/NIB-140085","article-title":"Physiological, Immunological and Evolutionary Perspectives of Labor as an Inflammatory Process","volume":"5","year":"2014","journal-title":"Adv. Neuroimmune Biol."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"e03485","DOI":"10.1016\/j.heliyon.2020.e03485","article-title":"Comparison of fetal heart rate variability by symbolic dynamics at the third trimester of pregnancy and low-risk parturition","volume":"6","author":"Berg","year":"2020","journal-title":"Heliyon"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"S263","DOI":"10.1016\/j.ajog.2010.10.686","article-title":"666: Continuous remote fetal monitoring with MONICA AN24 during home induction of labor","volume":"204","author":"Rauf","year":"2011","journal-title":"Am. J. Obstet. Gynecol."},{"key":"ref_17","first-page":"1","article-title":"A Comprehensive Evaluation of the Predictive Abilities of Fetal Electrocardiogram-Derived Parameters during Labor in Newborn Acidemia: Our Institutional Experience","volume":"2018","author":"Tian","year":"2018","journal-title":"Biomed Res. Int."},{"key":"ref_18","doi-asserted-by":"crossref","unstructured":"Mas-Cabo, J., Ye-Lin, Y., Benalcazar-Parra, C., Alberola-Rubio, J., Perales, A., Garcia-Casado, J., and Prats-Boluda, G. (2017, January 21\u201323). Electrohysterogram Signals from Patients with Threatened Preterm Labor: Concentric Ring Electrode Vs Disk Electrode Recordings. Proceedings of the 10th International Conference on Bio-inspired Systems and Signal Processing, Porto, Portugal.","DOI":"10.5220\/0006155000780083"},{"key":"ref_19","doi-asserted-by":"crossref","unstructured":"Ye-Lin, Y., Garcia-Casado, J., Prats-Boluda, G., Alberola-Rubio, J., and Perales, A. (2014). Automatic identification of motion artifacts in EHG recording for robust analysis of uterine contractions. Comput. Math. Methods Med., 2014.","DOI":"10.1155\/2014\/470786"},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"2","DOI":"10.1016\/j.ejogrb.2009.02.016","article-title":"Monitoring the progress of pregnancy and labor using electromyography","volume":"144","author":"Schlembach","year":"2009","journal-title":"Eur. J. Obstet. Gynecol. Reprod. Biol."},{"key":"ref_21","doi-asserted-by":"crossref","unstructured":"Lange, L., Vaeggemose, A., Kidmose, P., Mikkelsen, E., Uldbjerg, N., and Johansen, P. (2014). Velocity and directionality of the electrohysterographic signal propagation. PLoS ONE, 9.","DOI":"10.1371\/journal.pone.0086775"},{"key":"ref_22","doi-asserted-by":"crossref","unstructured":"Costa, M., Goldberger, A.L., and Peng, C.K. (2005). Multiscale entropy analysis of biological signals. Phys. Rev. E Stat. Nonlinear Soft Matter Phys., 71.","DOI":"10.1103\/PhysRevE.71.021906"},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1016\/j.physrep.2018.06.001","article-title":"Surrogate data for hypothesis testing of physical systems","volume":"748","author":"Lancaster","year":"2018","journal-title":"Phys. Rep."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"77","DOI":"10.1016\/0167-2789(92)90102-S","article-title":"Testing for nonlinearity in time series: The method of surrogate data","volume":"58","author":"Theiler","year":"1992","journal-title":"Phys. D Nonlinear Phenom."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"635","DOI":"10.1103\/PhysRevLett.77.635","article-title":"Improved surrogate data for nonlinearity tests","volume":"77","author":"Schreiber","year":"1996","journal-title":"Phys. Rev. Lett."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"344","DOI":"10.1152\/japplphysiol.00059.2017","article-title":"Nonlinearities of heart rate variability in animal models of impaired cardiac control: Contribution of different time scales","volume":"123","author":"Silva","year":"2017","journal-title":"J. Appl. Physiol."},{"key":"ref_27","doi-asserted-by":"crossref","unstructured":"Vrhovec, J., Macek Lebar, A., and Rudel, D. (2007). Evaluating uterine electrohysterogram with entropy. IFMBE Proceedings, Springer.","DOI":"10.1007\/978-3-540-73044-6_36"},{"key":"ref_28","first-page":"1053","article-title":"Time series forecasting for non-linear and non-stationary processes: A review and comparative study","volume":"47","author":"Cheng","year":"2015","journal-title":"IIE Trans. (Institute Ind. Eng.)"},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"33","DOI":"10.1007\/s13194-012-0056-8","article-title":"What is a complex system?","volume":"3","author":"Ladyman","year":"2012","journal-title":"Eur. J. Philos. Sci."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"1198","DOI":"10.1111\/j.1471-0528.1989.tb03196.x","article-title":"Changes in the connective tissue of corpus and cervix uteri during ripening and labour in term pregnancy","volume":"96","author":"Ekman","year":"1989","journal-title":"BJOG An Int. J. Obstet. Gynaecol."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1530\/rep.0.1240001","article-title":"Prostaglandins and mechanisms of preterm birth","volume":"124","author":"Sloboda","year":"2002","journal-title":"Reproduction"},{"key":"ref_32","doi-asserted-by":"crossref","unstructured":"Ramachandra, M. (2009). Web-based Supply Chain Management and Digital Signal Processing: Methods for Effective Information Administration and Transmission, Business Science Reference.","DOI":"10.4018\/978-1-60566-888-8"},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"1371","DOI":"10.1109\/TBME.2002.804582","article-title":"Quantifying physiological data with Lempel-Ziv complexity - Certain issues","volume":"49","author":"Nagarajan","year":"2002","journal-title":"IEEE Trans. Biomed. Eng."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"2785","DOI":"10.1142\/S0218127400001870","article-title":"Testing for nonlinearity of the contraction segments in uterine electromyography","volume":"10","author":"Radhakrishnan","year":"2000","journal-title":"Int. J. Bifurcat. Chaos"},{"key":"ref_35","doi-asserted-by":"crossref","unstructured":"Hassan, M., Terrien, J., Alexandersson, A., Marque, C., and Karlsson, B. (September, January 31). Nonlinearity of EHG signals used to distinguish active labor from normal pregnancy contractions. Proceedings of the 2010 Annual International Conference of the IEEE Engineering in Medicine and Biology, Buenos Aires, Argentina.","DOI":"10.1109\/IEMBS.2010.5627413"},{"key":"ref_36","first-page":"A8535","article-title":"Electrohysterography. A promising alternative for monitoring contractions","volume":"159","author":"Vlemminx","year":"2015","journal-title":"Ned. Tijdschr. Geneeskd."},{"key":"ref_37","doi-asserted-by":"crossref","unstructured":"Monteiro-Santos, J., Henriques, T., Nunes, I., Amorim-Costa, C., Bernardes, J., and Costa-Santos, C. (2020). Complexity of cardiotocographic signals as a predictor of labor. Entropy, 22.","DOI":"10.3390\/e22010104"},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"401","DOI":"10.1007\/s11517-018-1888-y","article-title":"Uterine electromyography for discrimination of labor imminence in women with threatened preterm labor under tocolytic treatment","volume":"57","author":"Perales","year":"2019","journal-title":"Med. Biol. Eng. Comput."},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"98","DOI":"10.1016\/j.bspc.2018.05.016","article-title":"Open-access software for analysis of fetal heart rate signals","volume":"45","author":"Kocamaz","year":"2018","journal-title":"Biomed. Signal Process. Control"},{"key":"ref_40","doi-asserted-by":"crossref","unstructured":"Sbrollini, A., Agostinelli, A., Burattini, L., Morettini, M., Di Nardo, F., Fioretti, S., and Burattini, L. (2017, January 11\u201315). CTG Analyzer: A graphical user interface for cardiotocography. Proceedings of the 2017 39th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC), Seogwipo, Korea.","DOI":"10.1109\/EMBC.2017.8037391"},{"key":"ref_41","doi-asserted-by":"crossref","unstructured":"Vrhovec, J., and Lebar, A.M. (2012). An Uterine Electromyographic Activity as a Measure of Labor Progression. Appl. EMG Clin. Sport. Med., 243\u2013268.","DOI":"10.5772\/25526"}],"container-title":["Entropy"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1099-4300\/22\/8\/798\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T09:50:32Z","timestamp":1760176232000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1099-4300\/22\/8\/798"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2020,7,22]]},"references-count":41,"journal-issue":{"issue":"8","published-online":{"date-parts":[[2020,8]]}},"alternative-id":["e22080798"],"URL":"https:\/\/doi.org\/10.3390\/e22080798","relation":{},"ISSN":["1099-4300"],"issn-type":[{"value":"1099-4300","type":"electronic"}],"subject":[],"published":{"date-parts":[[2020,7,22]]}}}