{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,12]],"date-time":"2026-09-12T04:21:24Z","timestamp":1789186884939,"version":"build-2803163510"},"reference-count":18,"publisher":"Wiley","issue":"5","license":[{"start":{"date-parts":[[2011,5,3]],"date-time":"2011-05-03T00:00:00Z","timestamp":1304380800000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/onlinelibrary.wiley.com\/termsAndConditions#vor"}],"content-domain":{"domain":["obgyn.onlinelibrary.wiley.com"],"crossmark-restriction":true},"short-container-title":["Ultrasound in Obstet &amp; Gyne"],"published-print":{"date-parts":[[2011,11]]},"abstract":"<jats:title>Abstract<\/jats:title><jats:sec><jats:title>Objective<\/jats:title><jats:p>To determine the accuracy of ultrasound at 11\u201314 weeks' gestation in the diagnosis of chorionicity in twin pregnancy.<\/jats:p><\/jats:sec><jats:sec><jats:title>Methods<\/jats:title><jats:p>This was a retrospective observational study of data obtained between 1999 and 2010. At the first\u2010trimester routine ultrasound scan, chorionicity was assigned according to the number of placental masses and T or \u03bb\u2010signs for a single placental mass. Chorionicity was confirmed by histology or discordant sex at birth.<\/jats:p><\/jats:sec><jats:sec><jats:title>Results<\/jats:title><jats:p>A total of 648 pregnancies were assigned chorionicity by first\u2010trimester ultrasound during the study period. Chorionicity was ascertained in 613 cases, either by histology (<jats:italic>n<\/jats:italic> = 340) or discordant sex (<jats:italic>n<\/jats:italic> = 273). Chorionicity was correctly assigned by ultrasound at 11\u201314 weeks in 612 of 613 pregnancies (accuracy 99.8%). Sensitivity and specificity for determining monochorionicity were 100% and 99.8%, respectively.<\/jats:p><\/jats:sec><jats:sec><jats:title>Conclusions<\/jats:title><jats:p>First\u2010trimester ultrasound can be used to determine chorionicity reliably by noting the number of placental masses and T or \u03bb\u2010signs. Determination of twin chorionicity is important and should be completed in the first trimester. Copyright \u00a9 2011 ISUOG. Published by John Wiley &amp; Sons, Ltd.<\/jats:p><\/jats:sec>","DOI":"10.1002\/uog.8956","type":"journal-article","created":{"date-parts":[[2011,1,31]],"date-time":"2011-01-31T14:20:16Z","timestamp":1296483616000},"page":"530-532","update-policy":"https:\/\/doi.org\/10.1002\/crossmark_policy","source":"Crossref","is-referenced-by-count":94,"title":["First\u2010trimester ultrasound determination of chorionicity in twin pregnancy"],"prefix":"10.1002","volume":"38","author":[{"given":"T.","family":"Dias","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"T.","family":"Arcangeli","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"A.","family":"Bhide","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"R.","family":"Napolitano","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"S.","family":"Mahsud\u2010Dornan","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"B.","family":"Thilaganathan","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"311","published-online":{"date-parts":[[2011,5,3]]},"reference":[{"key":"e_1_2_5_2_2","first-page":"1","article-title":"Births: final data for 2003","volume":"54","author":"Martin JA","year":"2003","journal-title":"Natl Vital Stat Rep"},{"key":"e_1_2_5_3_2","unstructured":"Scottish Perinatal and Infant Mortality and Morbidity Report (SPIMMR) Scottish Health Statistics ISD Scottish Division and Scottish Programme for Clinical Effectiveness and Reproductive Health (SPCERH) Edinburgh2002; (www.isdscotland.org\/isd\/info)."},{"key":"e_1_2_5_4_2","doi-asserted-by":"publisher","DOI":"10.1111\/j.1471-0528.1997.tb10948.x"},{"key":"e_1_2_5_5_2","doi-asserted-by":"publisher","DOI":"10.1002\/uog.6396"},{"key":"e_1_2_5_6_2","unstructured":"American College of Obstetricians and Gynecologists.Multiple gestation: complicated twin triplet and high\u2010order multifetal pregnancy. 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