title: Absence of nasal bone and detection of trisomy 21.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Monni
authors.forename: Maria Angelica
authors.initials: MA
authors.lastname: Zoppi
authors.forename: Rosa Maria
authors.initials: RM
authors.lastname: Ibba
mesh_terms: D004314:Down Syndrome / Q000175:diagnosis*; D005260:Female; D006801:Humans; D008423:Maternal Age; D009295:Nasal Bone / Q000002:abnormalities*; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D018566:Pregnancy, High-Risk; D011296:Prenatal Diagnosis / Q000379:methods*; D012307:Risk Factors