title: Comparison of models of maternal age-specific risk for Down syndrome live births.
abstract: OBJECTIVE
  To display and compare the different published formulae that specify the association between maternal age and the risk of a Down syndrome live birth.
  
  
  METHODS
  Papers published since 1987 on the prevalence of Down syndrome live births in relation to maternal age were located using MEDLINE and the references given in other papers. The data series and the models fitted to them were plotted to obtain a visual idea of their similarities and differences.
  
  
  RESULTS
  The observed and modelled age-specific rates for Down syndrome births were remarkably similar in all published series of data for women up to the age of 35, were reasonably similar for women aged 35 to 45, but differed for women older than 45.
  
  
  CONCLUSIONS
  In practice, the overall small differences in age-related risk between the different studies did not materially affect the performance of antenatal screening for Down syndrome. If a choice is to be made, the analysis based on the National Down Syndrome Cytogenetic Register (NDSCR) has marginal advantages since it is based on the largest data set and the corresponding model fits the data well. More data is needed to clarify the pattern of risk with maternal age among women over 45 years of age.
authors.affiliation: Department of Environmental and Preventive Medicine, Wolfson Institute of Preventive Medicine, St Bartholomew's and the Royal London School of Medicine and Dentistry, Charterhouse Square, London EC1M 6BQ, UK. j.k.morris@qmul.ac.uk
authors.forename: J K
authors.initials: JK
authors.lastname: Morris
authors.forename: N J
authors.initials: NJ
authors.lastname: Wald
authors.forename: D E
authors.initials: DE
authors.lastname: Mutton
authors.forename: E
authors.initials: E
authors.lastname: Alberman
mesh_terms: D000328:Adult; D001723:Birth Rate; D004314:Down Syndrome / Q000453:epidemiology*; D005260:Female; D006801:Humans; D008423:Maternal Age; D008875:Middle Aged; D011247:Pregnancy; D018566:Pregnancy, High-Risk; D012042:Registries; D012307:Risk Factors