title: More invasive procedures are done to detect each case of Down's syndrome in younger women.
abstract: OBJECTIVE
  To evaluate the performance of first-trimester combined screening in 5-year periods according to maternal age in a low-risk population.
  
  
  METHODS
  A prospective study.
  
  
  METHODS
  Multicenter study in Finland.
  
  
  METHODS
  A total of 76949 voluntary women with singleton pregnancies participated in first-trimester combined screening in public healthcare between 1 May 2002 and 31 December 2008.
  
  
  METHODS
  The serum samples were analyzed using the PerkinElmer AutoDELFIA® time-resolved fluoroimmunoassay kit for the measurement of pregnancy-associated plasma protein-A and free beta-human chorionic gonadotropin. Nuchal translucency was measured by trained personnel (midwives or physicians) in a university or central hospital.
  
  
  METHODS
  Performance, detection rate, false positive rate and the number of invasive procedures needed to detect a single case of Down's syndrome were analyzed.
  
  
  RESULTS
  There was a direct connection between maternal age and the prevalence of Down's syndrome with a low prevalence in young women being 1:1 193 in the 25-29 age group and 1:150 in the 35-39 age group. Consequently, for a fixed false positive rate of 5%, the number of invasive procedures needed to detect one case of Down's syndrome is higher in younger women to achieve the same detection rate.
  
  
  CONCLUSIONS
  In combined first trimester screening the risk for Down's syndrome is individual, varying with maternal age. This should be taken into consideration when counseling women.
authors.affiliation: Department of Obstetrics and Gynecology, Oulu University Hospital, Oulu, Finland.
authors.forename: Jaana
authors.initials: J
authors.lastname: Marttala
authors.forename: Jenni K
authors.initials: JK
authors.lastname: Ranta
authors.forename: Marja
authors.initials: M
authors.lastname: Kaijomaa
authors.forename: Pentti
authors.initials: P
authors.lastname: Nieminen
authors.forename: Paivi
authors.initials: P
authors.lastname: Laitinen
authors.forename: Hannaleena
authors.initials: H
authors.lastname: Kokkonen
authors.forename: Jarkko
authors.initials: J
authors.lastname: Romppanen
authors.forename: Esa
authors.initials: E
authors.lastname: Hamalainen
authors.forename: Johanna
authors.initials: J
authors.lastname: Kultti
authors.forename: Aydin
authors.initials: A
authors.lastname: Tekay
authors.forename: Veli-Matti
authors.initials: VM
authors.lastname: Ulander
authors.forename: Timppa
authors.initials: T
authors.lastname: Honkasalo
authors.forename: Markku
authors.initials: M
authors.lastname: Ryynanen
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000097:blood; D018997:Chorionic Gonadotropin, beta Subunit, Human / Q000097:blood; D004314:Down Syndrome / Q000097:blood* / Q000175:diagnosis*; D042241:Early Diagnosis; D005189:False Positive Reactions; D005260:Female; D005387:Finland; D005865:Gestational Age; D006801:Humans; D008423:Maternal Age; D008875:Middle Aged; D048208:Nuchal Translucency Measurement; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D011266:Pregnancy-Associated Plasma Protein-A / Q000378:metabolism; D011296:Prenatal Diagnosis / Q000379:methods*; D015995:Prevalence; D011446:Prospective Studies; D012307:Risk Factors
chemical_list: D015415:Biomarkers; D018997:Chorionic Gonadotropin, beta Subunit, Human; D011266:Pregnancy-Associated Plasma Protein-A