title: Prenatal screening and the reduction of birth defects in populations.
abstract: OBJECTIVE
  Birth defects occur in populations in 3-5% of births. This paper assesses whether population-wide screening programmes for pregnant women would be likely to result in major decreases in the prevalence of birth defects.
  
  
  METHODS
  Relevant literature on this question is reviewed and synthesized.
  
  
  RESULTS
  Given certain assumptions, a decrease from 3-5 to 2-4% in the prevalence of defects at birth may be possible. The resources required to put in place an appropriately delivered programme to achieve this are substantial.
  
  
  CONCLUSIONS
  As well as the potential benefit of a decrease, there are opportunity costs, and potential serious harms. Unless undertaken in a carefully planned and monitored way, a population-based birth defects reduction programme is likely to bring harm and anxiety rather than benefit.
authors.affiliation: Department of Medical Genetics, University of British Columbia, Vancouver, Canada. pbaird@unixg.ubc.ca
authors.forename: P A
authors.initials: PA
authors.lastname: Baird