title: Risk calculation of fetal chromosomal defects in the first trimester.
authors.forename: E
authors.initials: E
authors.lastname: Merz
mesh_terms: D000013:Congenital Abnormalities / Q000000981:diagnostic imaging* / Q000196:embryology* / Q000453:epidemiology; D005260:Female; D006801:Humans; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D012307:Risk Factors; D014463:Ultrasonography