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First-trimester contingent screening for trisomies 21, 18 and 13 by biomarkers and maternal blood cell-free DNA testing.
Nicolaides KH, Syngelaki A, Poon LC, Gil M, Wright D.
Fetal Diagn Ther 2014;35:185-92. pdf -
Nuchal translucency and other first-trimester sonographic markers of chromosomal abnormalities.
Nicolaides KH.
Am J Obstet Gynecol 2004;191:45-67.