title: Impact of a new national screening policy for Down's syndrome in Denmark: population based cohort study.
abstract: OBJECTIVE
  To evaluate the impact of a screening strategy in the first trimester, introduced in Denmark during 2004-6, on the number of infants born with Down's syndrome and the number of chorionic villus samplings and amniocenteses, and to determine detection and false positive rates in the screened population in 2005 and 2006.
  
  
  METHODS
  Population based cohort study.
  
  
  METHODS
  19 Danish departments of gynaecology and obstetrics and a central cytogenetic registry 2000-7.
  
  
  METHODS
  65 000 pregnancies per year.
  
  
  METHODS
  The primary outcomes measured were number of fetuses and newborn infants with Down's syndrome diagnosed prenatally and postnatally and number of chorionic villus samplings and amniocenteses carried out. Secondary outcomes measured were number of women screened in 2005 and 2006, screen positive rate, and information on screening in 2005 and 2006 for infants with a postnatal diagnosis of Down's syndrome.
  
  
  RESULTS
  The number of infants born with Down's syndrome decreased from 55-65 per year during 2000-4 to 31 in 2005 and 32 in 2006. The total number of chorionic villus samplings and amniocenteses carried out decreased from 7524 in 2000 to 3510 in 2006. The detection rate in the screened population in 2005 was 86% (95% confidence interval 79% to 92%) and in 2006 was 93% (87% to 97%). The corresponding false positive rates were 3.9% (3.7% to 4.1%) and 3.3% (3.1% to 3.4%).
  
  
  CONCLUSIONS
  The introduction of a combined risk assessment during the first trimester at a national level in Denmark halved the number of infants born with Down's syndrome. The strategy also resulted in a sharp decline in the number of chorionic villus samplings and amniocenteses carried out, even before full implementation of the policy.
authors.affiliation: Department of Fetal Medicine, Rigshospitalet, Copenhagen University Hospital, 2100 Copenhagen, Denmark.
authors.forename: Charlotte K
authors.initials: CK
authors.lastname: Ekelund
authors.forename: Finn Stener
authors.initials: FS
authors.lastname: Jørgensen
authors.forename: Olav Bjørn
authors.initials: OB
authors.lastname: Petersen
authors.forename: Karin
authors.initials: K
authors.lastname: Sundberg
authors.forename: Ann
authors.initials: A
authors.lastname: Tabor
mesh_terms: D000328:Adult; D000649:Amniocentesis / Q000379:methods; D015193:Chorionic Villi Sampling / Q000379:methods; D015331:Cohort Studies; D003718:Denmark; D004314:Down Syndrome / Q000175:diagnosis* / Q000517:prevention & control; D005260:Female; D006291:Health Policy; D006801:Humans; D007231:Infant, Newborn; D008403:Mass Screening / Q000379:methods*; D008423:Maternal Age; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D011296:Prenatal Diagnosis / Q000379:methods