title: [Analysis of prenatal follow-up strategies for trisomy 21 affected pregnancies in France].
abstract: OBJECTIVE
  The main objective of this study was to screen the prenatal follow-up of women with live birth trisomy 21 child in order to evaluate the proportion of prenatal screening failure versus cases where the women refused either the screening or the prenatal diagnosis of Down syndrome. This study covers the period of time from 2009 to 2012 when the national prenatal screening policy changed from second to first trimester and allows for a comparative assessment of the nationwide efficiency of the various maternal serum marker based strategies.
  
  
  METHODS
  All authorized cytogenetic laboratories sent required data for all cases of trisomy 21 diagnosed in FRANCE in new-borns (less than 1-year-old) from January 2010 to July 2013.
  
  
  RESULTS
  A total of 1253 cases of trisomy 21 were diagnosed before 1 year of age whose mother did not had prenatal diagnosis. For 861 of them, information on the prenatal follow-up was available, with 72% of cases where a prenatal screening was organized either by maternal serum marker or by ultrasound. Results of the screening strategy was positive with maternal serum marker in 28% of cases (calculated risk≥1/250), positive because of abnormal ultrasound in 5% and negative with maternal marker screening (whatever the strategy used) in 67% of cases. Detection rate over the period of the study was 82%, with similar efficiency of first and second trimester strategies (83%) but significantly lower with sequential association of first trimester Nuchal translucency measurement and second trimester serum screening (70%).
  
  
  CONCLUSIONS
  Switching from second trimester to first trimester screening strategy, with as many trisomy 21 foetuses diagnosed with half invasive procedures fulfilled national health policy objectives. Analysis of these data gives useful insights to elaborate a future screening policy involving cell-free foetal DNA sequencing.
authors.affiliation: Association des cytogénéticiens de langue française, France; Laboratoire de cytogénétique, HUPC hôpital Cochin, AP-HP, université Paris Descartes, Paris, France. Electronic address: jean-michel.dupont@aphp.fr.
authors.forename: J-M
authors.initials: JM
authors.lastname: Dupont
authors.affiliation: Association des cytogénéticiens de langue française, France; Laboratoire de biologie, CH de Versailles, Versailles, France.
authors.forename: B
authors.initials: B
authors.lastname: Simon-Bouy
authors.affiliation: Agence de la biomédecine, France.
authors.forename: A
authors.initials: A
authors.lastname: Zebina
authors.affiliation: Agence de la biomédecine, France.
authors.forename: F
authors.initials: F
authors.lastname: Pessione
authors.affiliation: Agence de la biomédecine, France.
authors.forename: D
authors.initials: D
authors.lastname: Royère
authors.affiliation: Association des cytogénéticiens de langue française, France; EA 3801, service de génétique, CHU de Reims, UFR de médecine, Reims, France.
authors.forename: M
authors.initials: M
authors.lastname: Doco-Fenzy
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000097:blood; D004314:Down Syndrome / Q000175:diagnosis* / Q000235:genetics; D005188:False Negative Reactions; D005260:Female; D005602:France; D005865:Gestational Age; D006291:Health Policy; D006801:Humans; D008423:Maternal Age; D048208:Nuchal Translucency Measurement; D017410:Practice Guidelines as Topic; D011247:Pregnancy; D011256:Pregnancy Outcome; D011261:Pregnancy Trimester, First; D011262:Pregnancy Trimester, Second; D011296:Prenatal Diagnosis / Q000379:methods / Q000706:statistics & numerical data*; D017422:Sequence Analysis, DNA; D016216:Ultrasonography, Prenatal
chemical_list: D015415:Biomarkers
keywords: ADN fœtal circulant; Cell-free foetal DNA; Dépistage; Marqueurs sériques maternels; Maternal serum marker; Screening; Trisomie 21; Trisomy 21