{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,8]],"date-time":"2026-09-08T11:32:46Z","timestamp":1788867166575,"version":"build-2803163510"},"reference-count":30,"publisher":"Wiley","issue":"5","license":[{"start":{"date-parts":[[2020,2,4]],"date-time":"2020-02-04T00:00:00Z","timestamp":1580774400000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/onlinelibrary.wiley.com\/termsAndConditions#vor"}],"funder":[{"DOI":"10.13039\/501100004836","name":"Det Frie Forskningsr\u00e5d","doi-asserted-by":"publisher","award":["09\u2010069101"],"award-info":[{"award-number":["09\u2010069101"]}],"id":[{"id":"10.13039\/501100004836","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100002739","name":"Aarhus Universitets Forskningsfond","doi-asserted-by":"publisher","award":["2011\u201021872\u201088"],"award-info":[{"award-number":["2011\u201021872\u201088"]}],"id":[{"id":"10.13039\/501100002739","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["obgyn.onlinelibrary.wiley.com"],"crossmark-restriction":true},"short-container-title":["Acta Obstet Gynecol Scand"],"published-print":{"date-parts":[[2020,5]]},"abstract":"<jats:title>Abstract<\/jats:title><jats:sec><jats:title>Introduction<\/jats:title><jats:p>Hypertensive disorders of pregnancy, including gestational hypertension and preeclampsia, are leading causes of morbidity and mortality for both mother and fetus. It has been proposed that vitamin D affects a number of biological processes involved in the pathogenesis of hypertensive disorders of pregnancy. Therefore, a seasonal variation in the risk of these disorders might be expected in areas such as Denmark with marked seasonal variation in sunlight exposure. In this study, we aimed to evaluate the existence of this association.<\/jats:p><\/jats:sec><jats:sec><jats:title>Material and methods<\/jats:title><jats:p>We used information from a cohort of 50\u00a0665 previously healthy, nulliparous women with singleton pregnancies. All women gave birth between 1989 and 2010 at Aarhus University Hospital, Denmark. Logistic regression analyses combined with the cubic spline method were used to estimate the seasonal variation for each outcome: gestational hypertension\u00a0and preeclampsia, after adjusting for calendar time.<\/jats:p><\/jats:sec><jats:sec><jats:title>Results<\/jats:title><jats:p>Of the 50\u00a0665 women included, 8.5% were diagnosed with a hypertensive disorder of pregnancy. The overall tendency was towards increasing risk when conceiving during spring and early summer, peaking midsummer, and subsequently decreasing steadily during late summer and fall to reach the nadir by winter. Seasonal variation was found for; gestational hypertension (<jats:italic>P<\/jats:italic>\u00a0=\u00a0.01); preeclampsia (<jats:italic>P<\/jats:italic>\u00a0=\u00a0.001) and early\u2010onset preeclampsia (<jats:italic>P<\/jats:italic>\u00a0=\u00a0.014).<\/jats:p><\/jats:sec><jats:sec><jats:title>Conclusions<\/jats:title><jats:p>We found a seasonal variation in the risk of the hypertensive disorders of pregnancy in a large cohort of Danish nulliparous women. The highest risk was seen in women with the estimated date of conception in June and August, that is, during summer. Seasonal variation in vitamin D status may explain this association.<\/jats:p><\/jats:sec>","DOI":"10.1111\/aogs.13786","type":"journal-article","created":{"date-parts":[[2020,2,5]],"date-time":"2020-02-05T05:01:44Z","timestamp":1580878904000},"page":"623-630","update-policy":"https:\/\/doi.org\/10.1002\/crossmark_policy","source":"Crossref","is-referenced-by-count":25,"title":["Seasonal variation in the hypertensive disorders of pregnancy in Denmark"],"prefix":"10.1111","volume":"99","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-5295-6923","authenticated-orcid":false,"given":"Christine","family":"Rohr Thomsen","sequence":"first","affiliation":[{"name":"Department of Obstetrics and Gynecology Aarhus University Hospital Aarhus Denmark"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6933-8294","authenticated-orcid":false,"given":"Tine","family":"Brink Henriksen","sequence":"additional","affiliation":[{"name":"Perinatal Epidemiology Research Unit Institute of Clinical Medicine &amp; Department of Pediatrics Aarhus University Hospital Aarhus Denmark"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6449-6426","authenticated-orcid":false,"given":"Niels","family":"Uldbjerg","sequence":"additional","affiliation":[{"name":"Department of Obstetrics and Gynecology Aarhus University Hospital Aarhus Denmark"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2640-7848","authenticated-orcid":false,"given":"Ioanna","family":"Milidou","sequence":"additional","affiliation":[{"name":"Department of Pediatrics Hospitals of West Jutland Herning Denmark"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"311","published-online":{"date-parts":[[2020,2,4]]},"reference":[{"key":"e_1_2_10_2_1","doi-asserted-by":"publisher","DOI":"10.5694\/j.1326-5377.2005.tb06730.x"},{"key":"e_1_2_10_3_1","doi-asserted-by":"publisher","DOI":"10.1016\/S0140-6736(10)60279-6"},{"key":"e_1_2_10_4_1","doi-asserted-by":"publisher","DOI":"10.1186\/s12884-017-1408-3"},{"key":"e_1_2_10_5_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.jri.2009.02.005"},{"key":"e_1_2_10_6_1","doi-asserted-by":"publisher","DOI":"10.1111\/j.1753-4887.2005.tb00378.x"},{"key":"e_1_2_10_7_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.jsgi.2004.02.002"},{"key":"e_1_2_10_8_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.mam.2008.08.005"},{"key":"e_1_2_10_9_1","doi-asserted-by":"publisher","DOI":"10.1111\/j.1365-2265.2010.03894.x"},{"key":"e_1_2_10_10_1","doi-asserted-by":"publisher","DOI":"10.1038\/ejcn.2013.3"},{"key":"e_1_2_10_11_1","doi-asserted-by":"publisher","DOI":"10.1136\/bmj.307.6898.234"},{"key":"e_1_2_10_12_1","doi-asserted-by":"publisher","DOI":"10.1016\/S0140-6736(05)17987-2"},{"key":"e_1_2_10_13_1","doi-asserted-by":"publisher","DOI":"10.1007\/s11892-015-0579-4"},{"key":"e_1_2_10_14_1","doi-asserted-by":"publisher","DOI":"10.1007\/s00404-014-3176-x"},{"issue":"3","key":"e_1_2_10_15_1","first-page":"167","article-title":"Association of maternal vitamin D and placenta growth factor with the diagnosis of early onset severe preeclampsia","volume":"30","author":"Robinson CJ","year":"2013","journal-title":"Am J Perinatol"},{"key":"e_1_2_10_16_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.cmpb.2011.07.016"},{"key":"e_1_2_10_17_1","doi-asserted-by":"publisher","DOI":"10.1371\/journal.pone.0094432"},{"key":"e_1_2_10_18_1","doi-asserted-by":"publisher","DOI":"10.1097\/01.ede.0000254064.92806.13"},{"key":"e_1_2_10_19_1","doi-asserted-by":"publisher","DOI":"10.1186\/1471-2393-14-69"},{"key":"e_1_2_10_20_1","unstructured":"The Danish National Archives.https:\/\/www.sa.dk\/en\/. 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