{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,17]],"date-time":"2026-06-17T16:18:18Z","timestamp":1781713098954,"version":"3.54.5"},"reference-count":27,"publisher":"Wiley","issue":"9","license":[{"start":{"date-parts":[[2023,7,7]],"date-time":"2023-07-07T00:00:00Z","timestamp":1688688000000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by-nc-nd\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100001840","name":"Icelandic Centre for Research","doi-asserted-by":"publisher","id":[{"id":"10.13039\/501100001840","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":[[2023,9]]},"abstract":"<jats:title>Abstract<\/jats:title><jats:sec><jats:title>Introduction<\/jats:title><jats:p>There is limited evidence about changes in the pelvic floor during active labor. We aimed to investigate changes in hiatal dimensions during the active first stage of labor and associations with fetal descent and head position.<\/jats:p><\/jats:sec><jats:sec><jats:title>Material and methods<\/jats:title><jats:p>We conducted a longitudinal, prospective cohort study at the National University Hospital of Iceland, from 2016 to 2018. Nulliparous women with spontaneous onset of labor, a single fetus in cephalic presentation, and gestational age \u226537\u2009weeks were eligible. Fetal position was assessed with transabdominal ultrasound and fetal descent was measured with transperineal ultrasound. Three\u2010dimensional volumes were acquired from transperineal scanning at the start of the active phase of labor and in late first stage or early second stage. The largest transverse hiatal diameter was measured in the plane of minimal hiatal dimensions. The levator urethral gap was measured as the distance between the center of the urethra and the levator insertion using tomographic ultrasound imaging. Measurements of the levator urethral gap were made in the plane of minimal hiatal dimensions and 2.5 and 5\u2009mm cranial to this.<\/jats:p><\/jats:sec><jats:sec><jats:title>Results<\/jats:title><jats:p>The final study population comprised 78 women. The mean transverse hiatal diameter increased 12.4% between the two examinations, from 39.4\u2009\u00b1\u20094.1\u2009mm (\u00b1standard deviation) at the first examination to 44.3\u2009\u00b1\u20095.8\u2009mm at the last examination (<jats:italic>p<\/jats:italic>\u2009&lt;\u20090.01). We found a moderate correlation between the transverse hiatal diameter and fetal station at the last examination (<jats:italic>r<\/jats:italic>\u2009=\u20090.44, <jats:italic>r<\/jats:italic><jats:sup>2<\/jats:sup>\u2009=\u20090.19; <jats:italic>p<\/jats:italic>\u2009&lt;\u20090.01; regression equation <jats:italic>y<\/jats:italic>\u2009=\u20092.71\u2009+\u20090.014<jats:italic>x<\/jats:italic>), and a weak correlation between the change in transverse hiatal diameter and change in fetal station (<jats:italic>r<\/jats:italic>\u2009=\u20090.29; <jats:italic>r<\/jats:italic><jats:sup>2<\/jats:sup>\u2009=\u20090.08; <jats:italic>p<\/jats:italic>\u2009=\u20090.01; regression equation <jats:italic>y<\/jats:italic>\u2009=\u20090.24\u2009+\u20090.012<jats:italic>x<\/jats:italic>). Levator urethral gap increased significantly in all three planes on both the left and right sides. Head position was not associated with hiatal measurements after adjusting for fetal station.<\/jats:p><\/jats:sec><jats:sec><jats:title>Conclusions<\/jats:title><jats:p>We found a significant, but only modest, increase of the hiatal dimensions during the first stage of labor. The risk of levator ani trauma will therefore be low during this stage. The change in transverse hiatal diameter was associated with fetal descent but not with head position.<\/jats:p><\/jats:sec>","DOI":"10.1111\/aogs.14620","type":"journal-article","created":{"date-parts":[[2023,7,7]],"date-time":"2023-07-07T12:12:26Z","timestamp":1688731946000},"page":"1203-1209","update-policy":"https:\/\/doi.org\/10.1002\/crossmark_policy","source":"Crossref","is-referenced-by-count":6,"title":["Ultrasound examination of the pelvic floor during active labor: A longitudinal cohort study"],"prefix":"10.1111","volume":"102","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-3162-9595","authenticated-orcid":false,"given":"Torbj\u00f8rn M.","family":"Eggeb\u00f8","sequence":"first","affiliation":[{"name":"National Center for Fetal Medicine Trondheim University Hospital (St. Olavs Hospital)  Trondheim Norway"},{"name":"Institute of Clinical and Molecular Medicine Norwegian University of Science and Technology  Trondheim Norway"},{"name":"Department of Obstetrics and Gynecology Stavanger University Hospital  Stavanger Norway"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Sigurlaug","family":"Benediktsdottir","sequence":"additional","affiliation":[{"name":"Department of Obstetrics and Gynecology Landspitali University Hospital  Reykjavik Iceland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4984-7635","authenticated-orcid":false,"given":"Hulda","family":"Hjartardottir","sequence":"additional","affiliation":[{"name":"Department of Obstetrics and Gynecology Landspitali University Hospital  Reykjavik Iceland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1788-4063","authenticated-orcid":false,"given":"Kjell \u00c5.","family":"Salvesen","sequence":"additional","affiliation":[{"name":"National Center for Fetal Medicine Trondheim University Hospital (St. Olavs Hospital)  Trondheim Norway"},{"name":"Institute of Clinical and Molecular Medicine Norwegian University of Science and Technology  Trondheim Norway"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9392-1674","authenticated-orcid":false,"given":"Ingrid","family":"Voll\u00f8yhaug","sequence":"additional","affiliation":[{"name":"Institute of Clinical and Molecular Medicine Norwegian University of Science and Technology  Trondheim Norway"},{"name":"Department of Obstetrics and Gynecology Trondheim University Hospital (St. Olavs Hospital)  Trondheim Norway"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"311","published-online":{"date-parts":[[2023,7,7]]},"reference":[{"key":"e_1_2_9_2_1","first-page":"244","article-title":"Pelvic anatomy. 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