20.500.12556/RUL-187797 Circadian characteristics of term and preterm labors The labor is a physiological event considered to have its own circadian (diurnal) rhythm, but some of the data remain conflicting, especially for preterm births. In this retrospective study, we analyzed the circadian trends of labor onset times in the Slovenian birth cohort from 1990 to 2018 with over 550,000 cases of singleton births. The number of term and preterm labor onsets was calculated for each hour in a day and circadian trends were evaluated for each of the study groups by modeling with a generalized Poisson distribution linked with the cosinor regression model using logarithmic link function. The induced labors were taken as the control group since the timing of labor depends mostly on the working schedule of personnel and not on the intrinsic rhythmic characteristics. For induced labors, the main peak in the number of labor cases was observed in the late morning hours (around 10 AM) for all gestational ages. The prominence of this peak becomes smaller in spontaneous premature labors with gradually disrupting rhythmicity in very preterm and extremely preterm cases. Labors starting with spontaneous contractions peak between 6 and 7 AM and lose the rhythmicity at 35 weeks of gestation while labors starting with a spontaneous rupture of membranes peak at 1 AM and lose the rhythmicity at 31 weeks of gestation, suggesting differences in underlying mechanisms. According to our knowledge, this is the first study that shows differences of circadian trends between different types of spontaneous labors, i.e., labors initiated with contraction and labors initiated with a spontaneous rupture of membranes. Moreover, the obtained results represent evidence of gradual disruption of rhythmicity from mild to extreme prematurity. preterm birth spontaneous birth circadian rhythms cosinor model prezgodnji porod spontani porod cirkadiani ritmi model Cosinor true false true Angleški jezik Slovenski jezik Članek v reviji 2026-09-14 14:07:16 2026-09-14 14:07:20 2026-09-16 03:50:58 0000-00-00 00:00:00 2024 0 0 12 str. iss. 1, art. 4033 Vol. 14 2024 0000-00-00 Zaloznikova Objavljeno NiDoloceno 0000-00-00 0000-00-00 0000-00-00 618.2/.7 2045-2322 10.1038/s41598-024-54490-2 187262467 RAZ_Moskon_Miha_2024.pdf RAZ_Moskon_Miha_2024.pdf 1 EE598769393426912ABFC7DA1639F280 46f871f50bc38e5ba6eccd3ac461c6bcd8df86a3a07eb3f53a00eddd40e8d2bb 25fc8a3f-b035-11f1-8bc5-0050569b8976 https://repozitorij.uni-lj.si/Dokument.php?lang=slv&id=247562 https://www.nature.com/articles/s41598-024-54490-2 1 d220242f-b034-11f1-8bc5-0050569b8976 https://repozitorij.uni-lj.si/Dokument.php?lang=slv&id=247561 Medicinska fakulteta 0 0 0