{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,30]],"date-time":"2026-06-30T15:30:53Z","timestamp":1782833453255,"version":"3.54.5"},"reference-count":16,"publisher":"Wiley","issue":"5","license":[{"start":{"date-parts":[[2020,10,13]],"date-time":"2020-10-13T00:00:00Z","timestamp":1602547200000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by-nc-nd\/4.0\/"}],"content-domain":{"domain":["obgyn.onlinelibrary.wiley.com"],"crossmark-restriction":true},"short-container-title":["Ultrasound in Obstet &amp;amp; Gyne"],"published-print":{"date-parts":[[2020,11]]},"abstract":"<jats:title>ABSTRACT<\/jats:title><jats:sec><jats:title>Objectives<\/jats:title><jats:p>The majority of cases of placenta previa or a low\u2010lying placenta in the second trimester will have a normal placental position in the third trimester. The aim of this study was to assess the accuracy of the distance between the placenta and the internal os of the cervix (IOD) in the second trimester for the prediction of third\u2010trimester low\u2010positioned placenta, and to define a cut\u2010off value at which all cases of third\u2010trimester low\u2010positioned placenta are identified.<\/jats:p><\/jats:sec><jats:sec><jats:title>Methods<\/jats:title><jats:p>This was a prospective cohort study including women undergoing a transvaginal ultrasound examination between 18 and 24\u2009weeks' gestation who had a low\u2010positioned placenta, defined as an IOD of &lt;\u200920\u2009mm. Low\u2010positioned placenta included placenta previa, defined as a placenta covering the internal os of the cervix, and a low\u2010lying placenta, defined as a placenta lying near to (within 20\u2009mm) but not overlying the internal os. All women were re\u2010evaluated in the third trimester. Relative risks for a low\u2010positioned placenta in the third trimester were calculated for women with placenta previa <jats:italic>vs<\/jats:italic> a low\u2010lying placenta, posterior <jats:italic>vs<\/jats:italic> anterior placenta and positive <jats:italic>vs<\/jats:italic> negative history of Cesarean section. Multilevel likelihood ratios for ranges of IOD in the prediction of a low\u2010positioned placenta in the third trimester were calculated separately for anteriorly and posteriorly located placentae. Corresponding receiver\u2010operating\u2010characteristics curves were constructed.<\/jats:p><\/jats:sec><jats:sec><jats:title>Results<\/jats:title><jats:p>In total, 958 women were included in the study. In the second trimester, placentae were more frequently located on the posterior side (62.0%) than on the anterior side (38.0%). In the third trimester, 48\/958 (5.0%) placentae persisted as a low\u2010positioned placenta. Women with placenta previa in the second trimester had a higher risk of a low\u2010positioned placenta in the third trimester than did those with a low\u2010lying placenta in the second trimester (37\/181 (20.4%) <jats:italic>vs<\/jats:italic> 11\/777 (1.4%); relative risk (RR), 17.9 (95%\u2009CI, 8.9\u201336.0)). Women with a posterior placenta had a higher risk of a low\u2010positioned placenta in the third trimester than did those with an anterior placenta (38\/594 (6.4%) <jats:italic>vs<\/jats:italic> 10\/364 (2.7%); RR, 2.4 (95%\u2009CI, 1.2\u20134.9)), as did women with a history of Cesarean section compared with those without such a history (14\/105 (13.3%) <jats:italic>vs<\/jats:italic> 34\/853 (4.0%); RR, 3.7 (95%\u2009CI, 1.9\u20137.2)). The cut\u2010off value of IOD in the second trimester to identify all cases of an abnormally located placenta in the third trimester was 15.5\u2009mm for posteriorly located placentae, while for anteriorly located placentae the IOD cut\u2010off was lower, namely \u20134.5\u2009mm, representing a 4.5\u2010mm overlap of the placental edge over the internal os of the cervix.<\/jats:p><\/jats:sec><jats:sec><jats:title>Conclusions<\/jats:title><jats:p>With incorporation of a safety margin of 5\u2009mm and ensuring that all women with placenta previa undergo a follow\u2010up scan, we recommend lowering the IOD cut\u2010off value for follow\u2010up in cases of an anterior low\u2010positioned placenta from 20 to 5\u2009mm, which would decrease the number of unnecessary follow\u2010up ultrasound examinations without missing any high\u2010risk women. \u00a9 2019 The Authors. <jats:italic>Ultrasound in Obstetrics &amp; Gynecology<\/jats:italic> published by John Wiley &amp; Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.<\/jats:p><\/jats:sec>","DOI":"10.1002\/uog.21903","type":"journal-article","created":{"date-parts":[[2019,10,31]],"date-time":"2019-10-31T22:43:52Z","timestamp":1572561832000},"page":"725-731","update-policy":"https:\/\/doi.org\/10.1002\/crossmark_policy","source":"Crossref","is-referenced-by-count":24,"title":["Follow\u2010up ultrasound in second\u2010trimester low\u2010positioned anterior and posterior placentae: prospective cohort study"],"prefix":"10.1002","volume":"56","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-2390-1245","authenticated-orcid":false,"given":"C. H. J. R.","family":"Jansen","sequence":"first","affiliation":[{"name":"Amsterdam UMC, University of Amsterdam, Department of Obstetrics and Gynaecology  Amsterdam The Netherlands"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"C. E.","family":"Kleinrouweler","sequence":"additional","affiliation":[{"name":"Amsterdam UMC, University of Amsterdam, Department of Obstetrics and Gynaecology  Amsterdam The Netherlands"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"A. W.","family":"Kastelein","sequence":"additional","affiliation":[{"name":"Amsterdam UMC, University of Amsterdam, Department of Obstetrics and Gynaecology  Amsterdam The Netherlands"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"L.","family":"Ruiter","sequence":"additional","affiliation":[{"name":"Amsterdam UMC, University of Amsterdam, Department of Obstetrics and Gynaecology  Amsterdam The Netherlands"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"E.","family":"van Leeuwen","sequence":"additional","affiliation":[{"name":"Amsterdam UMC, University of Amsterdam, Department of Obstetrics and Gynaecology  Amsterdam The Netherlands"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8337-550X","authenticated-orcid":false,"given":"B. W.","family":"Mol","sequence":"additional","affiliation":[{"name":"Monash University, Department of Obstetrics and Gynaecology  Clayton Victoria Australia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"E.","family":"Pajkrt","sequence":"additional","affiliation":[{"name":"Amsterdam UMC, University of Amsterdam, Department of Obstetrics and Gynaecology  Amsterdam The Netherlands"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"311","published-online":{"date-parts":[[2020,10,13]]},"reference":[{"key":"e_1_2_6_2_1","doi-asserted-by":"publisher","DOI":"10.1055\/s-2000-9269"},{"key":"e_1_2_6_3_1","doi-asserted-by":"publisher","DOI":"10.1016\/S0002-9378(11)90776-5"},{"key":"e_1_2_6_4_1","doi-asserted-by":"publisher","DOI":"10.1067\/mob.2003.10"},{"key":"e_1_2_6_5_1","doi-asserted-by":"publisher","DOI":"10.1111\/1471-0528.13829"},{"key":"e_1_2_6_6_1","doi-asserted-by":"publisher","DOI":"10.1097\/AOG.0000000000000245"},{"key":"e_1_2_6_7_1","doi-asserted-by":"publisher","DOI":"10.1016\/S1701-2163(16)32401-X"},{"key":"e_1_2_6_8_1","doi-asserted-by":"publisher","DOI":"10.1002\/jum.14554"},{"key":"e_1_2_6_9_1","doi-asserted-by":"publisher","DOI":"10.1111\/j.1471-0528.1990.tb02457.x"},{"key":"e_1_2_6_10_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.ejogrb.2019.06.020"},{"key":"e_1_2_6_11_1","doi-asserted-by":"publisher","DOI":"10.1016\/S0002-9378(84)80102-7"},{"key":"e_1_2_6_12_1","volume-title":"Clinical Epidemiology: How to do clinical practice research","author":"Haynes BR","year":"2006"},{"key":"e_1_2_6_13_1","doi-asserted-by":"publisher","DOI":"10.1002\/jcu.20427"},{"key":"e_1_2_6_14_1","first-page":"331","article-title":"Sonographic assessment of placental migration in second trimester low lying placenta","volume":"14","author":"Pradhan S","year":"2012","journal-title":"Nepal Med Coll J"},{"key":"e_1_2_6_15_1","doi-asserted-by":"publisher","DOI":"10.3109\/00016347709158351"},{"key":"e_1_2_6_16_1","doi-asserted-by":"publisher","DOI":"10.1007\/s11596-017-1745-5"},{"key":"e_1_2_6_17_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.clp.2011.03.010"}],"updated-by":[{"DOI":"10.1002\/uog.23547","type":"correction","label":"Correction","source":"publisher","updated":{"date-parts":[[2020,12,1]],"date-time":"2020-12-01T00:00:00Z","timestamp":1606780800000}}],"container-title":["Ultrasound in Obstetrics &amp; Gynecology"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/onlinelibrary.wiley.com\/doi\/pdf\/10.1002\/uog.21903","content-type":"application\/pdf","content-version":"vor","intended-application":"text-mining"},{"URL":"https:\/\/onlinelibrary.wiley.com\/doi\/full-xml\/10.1002\/uog.21903","content-type":"application\/xml","content-version":"vor","intended-application":"text-mining"},{"URL":"https:\/\/obgyn.onlinelibrary.wiley.com\/doi\/pdf\/10.1002\/uog.21903","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2023,8,25]],"date-time":"2023-08-25T22:05:45Z","timestamp":1693001145000},"score":1,"resource":{"primary":{"URL":"https:\/\/obgyn.onlinelibrary.wiley.com\/doi\/10.1002\/uog.21903"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2020,10,13]]},"references-count":16,"journal-issue":{"issue":"5","published-print":{"date-parts":[[2020,11]]}},"alternative-id":["10.1002\/uog.21903"],"URL":"https:\/\/doi.org\/10.1002\/uog.21903","archive":["Portico"],"relation":{"correction":[{"id-type":"doi","id":"10.1002\/uog.23547","asserted-by":"object"}]},"ISSN":["0960-7692","1469-0705"],"issn-type":[{"value":"0960-7692","type":"print"},{"value":"1469-0705","type":"electronic"}],"subject":[],"published":{"date-parts":[[2020,10,13]]},"assertion":[{"value":"2019-08-07","order":0,"name":"received","label":"Received","group":{"name":"publication_history","label":"Publication History"}},{"value":"2019-10-19","order":1,"name":"accepted","label":"Accepted","group":{"name":"publication_history","label":"Publication History"}},{"value":"2020-10-13","order":2,"name":"published","label":"Published","group":{"name":"publication_history","label":"Publication History"}}]}}