title: Has prenatal screening influenced the prevalence of comorbidities associated with Down syndrome and subsequent survival rates?
abstract: OBJECTIVE
  With this study we aimed to compare survival rates for children with Down syndrome in 2 time periods, 1 before prenatal screening (1988-1990) and 1 contemporaneous with screening (1998-2000), and to examine the frequency of comorbidities and their influence on survival rates.
  
  
  METHODS
  Record-linkage was performed between the population-based Victorian Birth Defects Register and records of deaths in children up to 15 years of age collected under the auspice of the Consultative Council on Obstetric and Pediatric Mortality and Morbidity. Cases of Down syndrome were coded according to the presence or absence of comorbidities by using the International Classification of Diseases, Ninth Revision classification of birth defects. Kaplan-Meier survival functions and log rank tests for equality of survival distributions were performed.
  
  
  RESULTS
  Of infants liveborn with Down syndrome in 1998-2000, 90% survived to 5 years of age, compared with 86% in the earlier cohort. With fetal deaths excluded, the proportion of isolated Down syndrome cases in the earlier cohort was 48.7% compared with 46.1% in the most recent cohort. In 1988-1990 there was at least 1 cardiac defect in 41.1% of cases and in 45.4% in 1998-2000. There was significant variation in survival rates for the different comorbidity groupings in the 1988-1990 cohort, but this was not so evident in the 1998-2000 cohort.
  
  
  CONCLUSIONS
  Survival of children with Down syndrome continues to improve, and there is an overall survival figure of 90% to at least 5 years of age. It is clear from this study that prenatal screening technologies are not differentially ascertaining fetuses with Down syndrome and additional defects, because there has been no proportional increase in births of isolated cases with Down syndrome.
authors.affiliation: Murdoch Childrens Research Institute, Parkville, Victoria, Australia. jane.halliday@mcri.edu.au
authors.forename: Jane
authors.initials: J
authors.lastname: Halliday
authors.forename: Veronica
authors.initials: V
authors.lastname: Collins
authors.forename: Merilyn
authors.initials: M
authors.lastname: Riley
authors.forename: Danielle
authors.initials: D
authors.lastname: Youssef
authors.forename: Evelyne
authors.initials: E
authors.lastname: Muggli
mesh_terms: D002675:Child, Preschool; D015331:Cohort Studies; D015897:Comorbidity; D016208:Databases, Factual / Q000639:trends; D004314:Down Syndrome / Q000175:diagnosis* / Q000453:epidemiology / Q000401:mortality*; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008403:Mass Screening / Q000379:methods / Q000639:trends; D011247:Pregnancy; D011296:Prenatal Diagnosis / Q000379:methods / Q000639:trends*; D015995:Prevalence; D015996:Survival Rate / Q000639:trends