{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,21]],"date-time":"2025-10-21T06:12:52Z","timestamp":1761027172756,"version":"build-2065373602"},"reference-count":54,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2025,10,21]],"date-time":"2025-10-21T00:00:00Z","timestamp":1761004800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["frontiersin.org"],"crossmark-restriction":true},"short-container-title":["Front. Med."],"abstract":"<jats:sec><jats:title>Background<\/jats:title><jats:p>To evaluate the association between seasonal temperature variations and clinical outcomes of <jats:italic>in vitro<\/jats:italic> fertilization (IVF), aiming to provide theoretical foundations for optimizing protocol timing in reproductive medicine.<\/jats:p><\/jats:sec><jats:sec><jats:title>Methods<\/jats:title><jats:p>This retrospective cohort study analyzed 2,551 first fresh IVF-embryo transfer (IVF-ET) cycles performed at a tertiary reproductive center of The First Affiliated Hospital of Shandong University of Traditional Chinese Medicine between January 2009 and January 2024. The study population comprised normo-ovulatory women aged &amp;lt; 35 years without uterine anomalies or severe male factor infertility (sperm concentration &amp;gt;1 \u00d7 106\/mL). Cycles were stratified into four seasonal cohorts based on gonadotropin initiation dates: spring (March-May, <jats:italic>n<\/jats:italic> = 709), summer (June-August, <jats:italic>n<\/jats:italic> = 787), autumn (September-November, <jats:italic>n<\/jats:italic> = 640), and winter (December-February, <jats:italic>n<\/jats:italic> = 415). Primary outcomes included clinical pregnancy rate (CPR), live birth rate (LBR), miscarriage rate (MR), and Full-Term delivery rate (FTBR), analyzed through multivariable logistic regression models adjusting for mean daily temperature (\u00b0C), relative humidity (%), and daylight hours (h).<\/jats:p><\/jats:sec><jats:sec><jats:title>Results<\/jats:title><jats:p>Compared with the winter control group, risk of miscarriage in cycles initiated in spring showed a statistically significant increase (95% CI 1.019, 2.846; <jats:italic>P<\/jats:italic> = 0.042). Although CPR showed no seasonal variation (spring: 54.30%, summer: 52.22%, autumn: 50.47%, winter: 50.36%; <jats:italic>P<\/jats:italic> = 0.464), the spring cohort exhibited a numerically higher Full-Term delivery rate (39.07 vs. 34.22%; <jats:italic>P<\/jats:italic> = 0.105). Sensitivity analysis using weighted analysis to balance sample sizes across groups revealed significantly higher full-term birth rates in spring compared to winter (<jats:italic>P<\/jats:italic> = 0.046) and the live birth rate in spring was also significantly higher than in winter (<jats:italic>P<\/jats:italic> = 0.029). For each unit increase in sunlight intensity on the trigger day, the probability of successful pregnancy decreases to approximately 0.978 times the original value (OR = 0.978 per lux-unit increase, 95% CI 0.960\u20130.997; <jats:italic>P<\/jats:italic> = 0.025).<\/jats:p><\/jats:sec><jats:sec><jats:title>Conclusion<\/jats:title><jats:p>Seasonal microenvironmental factors during ovarian stimulation may modulate IVF success trajectories, suggesting potential benefits of climate-adaptive protocol personalization in temperate monsoon regions.<\/jats:p><\/jats:sec><jats:sec><jats:title>Clinical trial registration<\/jats:title><jats:p>This is a retrospective case-control study.<\/jats:p><\/jats:sec>","DOI":"10.3389\/fmed.2025.1681770","type":"journal-article","created":{"date-parts":[[2025,10,21]],"date-time":"2025-10-21T05:38:54Z","timestamp":1761025134000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":0,"title":["The impact of seasonal variations on IVF pregnancy outcomes: a retrospective cohort study in Jinan, China"],"prefix":"10.3389","volume":"12","author":[{"given":"Xin","family":"Hu","sequence":"first","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Heng-bing","family":"Li","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jing-yan","family":"Song","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Hai-ning","family":"Yuan","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Ying","family":"Xu","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Kai-liang","family":"Ai","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Zhen-gao","family":"Sun","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Zhen-ni","family":"Mu","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1965","published-online":{"date-parts":[[2025,10,21]]},"reference":[{"key":"B1","doi-asserted-by":"publisher","first-page":"e2003926118","DOI":"10.1073\/pnas.2003926118","article-title":"Hormone seasonality in medical records suggests circannual endocrine circuits","volume":"118","author":"Tendler","year":"2021","journal-title":"Proc Natl Acad Sci USA."},{"key":"B2","doi-asserted-by":"publisher","first-page":"4073","DOI":"10.3390\/cells11244073","article-title":"Effects of heat stress on bovine oocytes and early embryonic development-an update","volume":"11","author":"Mietkiewska","year":"2022","journal-title":"Cells"},{"key":"B3","doi-asserted-by":"publisher","first-page":"77","DOI":"10.1038\/s41558-019-0632-4","article-title":"The impact of high ambient temperatures on delivery timing and gestational lengths","volume":"10","author":"Barreca","year":"2020","journal-title":"Nat. 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