TY - CHAP M1 - Book, Section TI - Sonography in Multiple Gestation A1 - Matias, Alexandra A1 - Jeanty, Philippe A1 - Anthony, Johnson A1 - Toy, Eugene C. A2 - Fleischer, Arthur C. A2 - Abramowicz, Jacques S. A2 - Gonçalves, Luis F. A2 - Manning, Frank A. A2 - Monteagudo, Ana A2 - Timor, Ilan E. A2 - Toy, Eugene C. PY - 2017 T2 - Fleischer's Sonography in Obstetrics and Gynecology: Textbook and Teaching Cases, 8e AB - Key TermsMonozygotic twins: a pregnancy of 2 fetuses derived from the same zygote that divided between the day of fertilization and the 14th day. They can have phenotypic and genotypic differences and can have either a dichorionic or a monochorionic placentation.Dizygotic twins: a pregnancy of 2 fetuses derived from 2 different zygotes, resulting from the fertilization of 2 oocytes from the same cycle. They always have a dichorionic placentation.Chorionicity: type of placentation in cases of multiple pregnancy defined by the number of chorions.Lambda sign: sonographic sign resulting from the juxtaposition of 2 layers of amnion and 2 layers of chorion in a dichorionic twin pregnancy. SN - PB - McGraw-Hill Education CY - New York, NY Y2 - 2024/03/29 UR - obgyn.mhmedical.com/content.aspx?aid=1151032845 ER -