title: Complete trisomy 21 vs translocation Down syndrome: a comparison of modes of ascertainment.
abstract: OBJECTIVE
  To compare the indications for invasive prenatal testing resulting in the detection of translocation Down syndrome and complete trisomy 21.
  
  
  METHODS
  This case control study was based on a large amniocentesis and chorionic villi samples database (n = 534,795). All specimens with translocation Down syndrome (n = 203) comprised the translocation group and were compared with a maternal age-matched group (4 to 1, n = 812) in which complete trisomy 21 was detected. Women with a normal karyotype were randomly selected (n = 812) and served as controls. Indications for invasive testing were compared among the 3 paired groups using χ(2) analysis.
  
  
  RESULTS
  There were no differences in the incidence of abnormal first- and second-trimester screening tests between the translocation Down syndrome and the complete trisomy 21 groups. History of prior aneuploidy was significantly more frequent in the translocation Down syndrome group, as compared with either complete trisomy 21 fetuses or normal controls.
  
  
  CONCLUSIONS
  Fetuses with translocation Down syndrome present with the same screening abnormalities as fetuses with complete trisomy 21.
authors.affiliation: Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, New York University School of Medicine, Lenox Hill Hospital, New York, NY, USA.
authors.forename: Eran
authors.initials: E
authors.lastname: Bornstein
authors.forename: Erez
authors.initials: E
authors.lastname: Lenchner
authors.forename: Alan
authors.initials: A
authors.lastname: Donnenfeld
authors.forename: Cristiano
authors.initials: C
authors.lastname: Jodicke
authors.forename: Sean M
authors.initials: SM
authors.lastname: Keeler
authors.forename: Sara
authors.initials: S
authors.lastname: Kapp
authors.forename: Michael Y
authors.initials: MY
authors.lastname: Divon
mesh_terms: D000328:Adult; D000649:Amniocentesis; D000782:Aneuploidy; D016022:Case-Control Studies; D015193:Chorionic Villi Sampling; D002891:Chromosomes, Human, Pair 21; D004314:Down Syndrome / Q000175:diagnosis* / Q000235:genetics; D005260:Female; D006801:Humans; D011247:Pregnancy; D011296:Prenatal Diagnosis / Q000379:methods*; D012189:Retrospective Studies; D014178:Translocation, Genetic