Estimation of the number of people with Down syndrome in Australia and New Zealand

Abstract

Purpose: Previous research estimated the effect of selective terminations on birth prevalence and population prevalence of people with Down syndrome (DS) in the United States and Europe. This study provides comparative data from Australia and New Zealand.

Method: The number of live births (LBs) with DS-in the absence of DS-related terminations of pregnancy-was estimated on the maternal age distribution in the general population. Actual LBs were modeled on registry data. We applied constructed survival curves to annual LBs to predict population numbers.

Results: For 2016-2020, we estimated 265 annual LBs with DS (1 in 1158) in Australia and 41 annual LBs (1 in 1450) in New Zealand. For this period, the reduction percentage-the net result of DS-related terminations on LB prevalence-was estimated at 66% for Australia, 71% for New Zealand, 62% for Europe (excluding the former East Bloc), and only 32% for the United States.

Conclusion: The total population of people with DS has been decreasing since 2000 in Europe (West Bloc) and 2011 in New Zealand owing, in large part, to increased selective terminations. By contrast, the population continues to increase, as of 2020, in Australia and the United States.

Keywords: Australia; Down syndrome; New Zealand; Prevalence; Trisomy 21.