title: Revised estimates of the maternal age specific live birth prevalence of Down's syndrome.
abstract: OBJECTIVE
  To revise the estimates of maternal age specific live birth prevalence of Down's syndrome in the absence of antenatal screening and selective termination using newly available data.
  
  
  METHODS
  Data were used from the National Down Syndrome Cytogenetic Register (NDSCR), which contains information on nearly all antenatally or postnatally diagnosed cases of Down's syndrome in which a karyotype was confirmed between 1989 and 1998 in England and Wales. It is the largest single series of data on the prevalence of Down's syndrome.
  
  
  CONCLUSIONS
  The prevalence does not continue increasing at an increasing rate with age above age 45 as has been previously assumed. Above this age the rate of increase declines with increasing age. The overall age pattern is sigmoidal. A new logit logistic model is proposed which fits the data well. The risk of a Down's syndrome live birth is given by: risk=1/(1+exp(7.330-4.211/(1+exp(-0.282x(age-37.23))))).
authors.affiliation: Department of Environmental and Preventive Medicine, Wolfson Institute of Preventive Medicine, St Bartholomew's, UK. j.k.morris@qmul.ac.uk
authors.forename: J K
authors.initials: JK
authors.lastname: Morris
authors.forename: D E
authors.initials: DE
authors.lastname: Mutton
authors.forename: E
authors.initials: E
authors.lastname: Alberman
mesh_terms: D004314:Down Syndrome / Q000453:epidemiology*; D004739:England / Q000453:epidemiology; D008423:Maternal Age; D015995:Prevalence; D014852:Wales / Q000453:epidemiology