title: Prospective first-trimester screening for trisomy 21 in 30,564 pregnancies.
abstract: OBJECTIVE
  This study was undertaken to evaluate the performance of a 1-stop clinic for first-trimester assessment of risk (OSCAR) for trisomy 21 by a combination of maternal age, fetal nuchal translucency (NT) thickness, and maternal serum-free ss- human chorionic gonadotrophin (hCG) and pregnancy-associated plasma protein-A (PAPP-A).
  
  
  METHODS
  OSCAR was carried out in 30,564 pregnancies at 11 to 13 + 6 weeks. Patient-specific risks for trisomy 21 and detection and false-positive rates were calculated.
  
  
  RESULTS
  The median maternal age was 34 (range 15-49) years. Chromosomal abnormalities were identified in 330 pregnancies, including 196 cases of trisomy 21. The estimated risk for trisomy 21 was 1 in 300 or greater in 7.5% of the normal pregnancies, in 93.4% of those with trisomy 21 and in 88.8% of those with other chromosomal defects.
  
  
  CONCLUSIONS
  The most effective method of screening for chromosomal defects is by first-trimester fetal NT and maternal serum biochemistry.
authors.affiliation: Harris Birthright Research Centre for Fetal Medicine, King's College Hospital, London, UK.
authors.forename: Kyriaki
authors.initials: K
authors.lastname: Avgidou
authors.forename: Aris
authors.initials: A
authors.lastname: Papageorghiou
authors.forename: Renu
authors.initials: R
authors.lastname: Bindra
authors.forename: Kevin
authors.initials: K
authors.lastname: Spencer
authors.forename: Kypros H
authors.initials: KH
authors.lastname: Nicolaides
mesh_terms: D000293:Adolescent; D000328:Adult; D018997:Chorionic Gonadotropin, beta Subunit, Human / Q000097:blood; D004314:Down Syndrome / Q000097:blood / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000453:epidemiology; D005189:False Positive Reactions; D005260:Female; D006801:Humans; D008131:London / Q000453:epidemiology; D008423:Maternal Age; D008875:Middle Aged; D009333:Neck / Q000000981:diagnostic imaging / Q000196:embryology; D011237:Predictive Value of Tests; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D011266:Pregnancy-Associated Plasma Protein-A / Q000378:metabolism; D011296:Prenatal Diagnosis; D011446:Prospective Studies; D014463:Ultrasonography
chemical_list: D018997:Chorionic Gonadotropin, beta Subunit, Human; D011266:Pregnancy-Associated Plasma Protein-A