• Down sysndrome;
  • incidence;
  • maternal age;
  • genetic counseling


Maternal age-specific risks of giving birth to a child with the Down syndrome (DS) are given by single-year age intervals. Such data are of value for more precise genetic counseling and in cost-benefit analyses of prenatal diagnosis programs. The data were obtained by linking records of children with DS at the British Columbia Health Surveillance Registry (BCHSR) to the appropriate birth registrations to derive maternal ages. The data related to 519 affected children out of a total of 354,880 live births in British Columbia between 1961 and 1970. The results, which are based on a high level of ascertainment, are compared to those reported in the only other published study relating to risks by single-year maternal age groupings, where completeness of ascertainment was estimated to be only 38%.