{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,5,29]],"date-time":"2026-05-29T13:38:42Z","timestamp":1780061922549,"version":"3.54.0"},"reference-count":21,"publisher":"MDPI AG","issue":"3","license":[{"start":{"date-parts":[[2015,3,2]],"date-time":"2015-03-02T00:00:00Z","timestamp":1425254400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100000923","name":"Australian Research Council","doi-asserted-by":"publisher","award":["LP100200184"],"award-info":[{"award-number":["LP100200184"]}],"id":[{"id":"10.13039\/501100000923","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Entropy"],"abstract":"<jats:p>Development of the foetal autonomic nervous system can be indirectly understood by looking at the changes in beat to beat variability in foetal heart rates. This study presents Tone-Entropy (T-E) analysis of foetal heart rate variability (HRV) at multiple lags (1\u20138) to understand the influence of gestational ages (early and late) on the development of the foetal autonomic nervous system (ANS). The analysis was based on foetal electrocardiograms (FECGs) of 46 healthy foetuses of 20\u201332 weeks (early group) and 22 foetuses of 35\u201341 weeks (late group). Tone represents sympatho-vagal balance and entropy the total autonomic activities. Results show that tone increases and entropy decreases at all lags for the late foetus group. On the other hand, tone decreases and entropy increases at lags 1\u20134 in the early foetus group. Increasing tone in late foetuses might represent significant maturation of sympathetic nervous systems because foetuses approaching to delivery period need increased sympathetic activity. T-E could be quantitative clinical index to determine the early foetuses from late ones on the basis of maturation of autonomic nervous system.<\/jats:p>","DOI":"10.3390\/e17031042","type":"journal-article","created":{"date-parts":[[2015,3,2]],"date-time":"2015-03-02T10:45:12Z","timestamp":1425293112000},"page":"1042-1053","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":6,"title":["Tone Entropy Analysis of Foetal Heart Rate Variability"],"prefix":"10.3390","volume":"17","author":[{"given":"Ahsan","family":"Khandoker","sequence":"first","affiliation":[{"name":"Biomedical Engineering Department, Khalifa University of Science, Technology and Research,  Abu Dhabi 127788, United Arab Emirates"},{"name":"Department of Electrical & Electronic Engineering, University of Melbourne, Melbourne, VIC 3010, Australia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Chandan","family":"Karmakar","sequence":"additional","affiliation":[{"name":"Biomedical Engineering Department, Khalifa University of Science, Technology and Research,  Abu Dhabi 127788, United Arab Emirates"},{"name":"Centre for Pattern Recognition and Data Analytics, Deakin University, VIC 3216, Australia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yoshitaka","family":"Kimura","sequence":"additional","affiliation":[{"name":"Institute of International Advanced Interdisciplinary Research, Tohoku University School of Medicine, Sendai 980-8577, Japan"},{"name":"Department of Gynecology and Obstetrics, Tohoku University Hospital, Sendai 980-8577, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Miyuki","family":"Endo","sequence":"additional","affiliation":[{"name":"Institute of International Advanced Interdisciplinary Research, Tohoku University School of Medicine, Sendai 980-8577, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Sayaka","family":"Oshio","sequence":"additional","affiliation":[{"name":"Institute of International Advanced Interdisciplinary Research, Tohoku University School of Medicine, Sendai 980-8577, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Marimuthu","family":"Palaniswami","sequence":"additional","affiliation":[{"name":"Biomedical Engineering Department, Khalifa University of Science, Technology and Research,  Abu Dhabi 127788, United Arab Emirates"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2015,3,2]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"92","DOI":"10.1159\/000020896","article-title":"Alteration in the low-frequency domain in power spectral analysis of fetal heart beat fluctuations","volume":"14","author":"Ohta","year":"1999","journal-title":"Fetal Diagn. 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