title: The lambda sign at 10-14 weeks of gestation as a predictor of chorionicity in twin pregnancies.
abstract: Chorionicity was prospectively determined in 369 twin pregnancies by ultrasound at 10-14 weeks of gestation. Pregnancies were classified as monochorionic if there was a single placental mass in the absence of the lambda sign at the inter-twin membrane-placental junction, and dichorionic if there was a single placental mass but the lambda sign was present, or the placentas were not adjacent to each other. In 81 (22%) cases, the pregnancies were classified as monochorionic and in 288 (78%) as dichorionic. Pregnancy outcome was available in 279 cases and all 63 of these pregnancies classified as monochorionic resulted in the delivery of same-sex twins. Similarly, all 100 different-sex pairs were correctly classified as dichorionic. These findings demonstrate the high reliability of ultrasound examination at 10-14 weeks of gestation in determining chorionicity in twin pregnancies.
authors.affiliation: Harris Birthright Research Centre for Fetal Medicine, King's College Hospital Medical School, London, UK.
authors.forename: W
authors.initials: W
authors.lastname: Sepulveda
authors.forename: N J
authors.initials: NJ
authors.lastname: Sebire
authors.forename: K
authors.initials: K
authors.lastname: Hughes
authors.forename: A
authors.initials: A
authors.lastname: Odibo
authors.forename: K H
authors.initials: KH
authors.lastname: Nicolaides
mesh_terms: D000328:Adult; D002823:Chorion / Q000000981:diagnostic imaging*; D005260:Female; D005865:Gestational Age; D006801:Humans; D011237:Predictive Value of Tests; D011247:Pregnancy; D011256:Pregnancy Outcome; D011261:Pregnancy Trimester, First; D011272:Pregnancy, Multiple; D015203:Reproducibility of Results; D012189:Retrospective Studies; D014427:Twins; D016216:Ultrasonography, Prenatal