title: Second trimester prenatal ultrasound and screening for Down syndrome.
authors.forename: Peter A
authors.initials: PA
authors.lastname: Benn
authors.forename: James F X
authors.initials: JF
authors.lastname: Egan
mesh_terms: D001774:Blood Chemical Analysis; D004314:Down Syndrome / Q000175:diagnosis*; D005260:Female; D006801:Humans; D008403:Mass Screening; D011247:Pregnancy; D011262:Pregnancy Trimester, Second / Q000097:blood; D016216:Ultrasonography, Prenatal