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Screening for trisomy 18 by maternal age, fetal nuchal translucency, free beta-human chorionic gonadotropin and pregnancy-associated plasma protein-A.
Kagan KO, Wright D, Maiz N, Pandeva I, Nicolaides KH.
Ultrasound Obstet Gynecol 2008;32:488-92. -
Screening for trisomy 18 by fetal nuchal translucency and maternal serum free beta -hCG and PAPP-A at 10-14 weeks of gestation.
Tul N, Spencer K, Noble P, Chan C, Nicolaides K.
Prenat Diagn 1999;19:1035-42.