title: Singleton versus duplicate assays in maternal serum screening.
authors.forename: P A
authors.initials: PA
authors.lastname: Benn
mesh_terms: D004314:Down Syndrome / Q000175:diagnosis*; D005189:False Positive Reactions; D005260:Female; D006801:Humans; D009436:Neural Tube Defects / Q000175:diagnosis*; D011247:Pregnancy; D011296:Prenatal Diagnosis / Q000379:methods*; D011786:Quality Control