title: Absence of nasal bone and detection of trisomy 21.
authors.forename: Tim M
authors.initials: TM
authors.lastname: Reynolds
mesh_terms: D004314:Down Syndrome / Q000175:diagnosis*; D005260:Female; D006801:Humans; D009295:Nasal Bone / Q000002:abnormalities*; D011247:Pregnancy; D011262:Pregnancy Trimester, Second; D015203:Reproducibility of Results; D016216:Ultrasonography, Prenatal / Q000379:methods*