Impact of prenatal screening and diagnostic testing on trends in Down syndrome births and terminations in Western Australia 1980 to 2013

© 2015 John Wiley & Sons, Ltd. Objective: To assess how prenatal screening and diagnostic testing have impacted the diagnosis, termination and birth prevalence of Down syndrome in Western Australia (1980-2013). Method: We analysed trends in termination rates and birth prevalence of Down syndrome using aggregated data (1980-2013). We modelled the expected live-birth rate and prevalence of Down syndrome and compared different eras of screening and diagnosis with respect to the impact on live-birth rate and prevalence of Down syndrome. Results: Between 1980 and 2013, the rate of Down syndrome pregnancies increased, corresponding to a greater proportion of babies born to older women. Following the introduction of screening in 1994, the rate of live-born infants with Down syndrome reduced significantly (p=0.001). The rate of terminations of pregnancy for Down syndrome remained stable over this period. In the absence of termination, the Down syndrome live-birth rate would have risen from 1.1 per 1000 to 2.17 per 1000 between 1980 and 2013. Conclusion: Prenatal testing in Western Australia has reduced the birth prevalence of Down syndrome despite an increased rate of Down syndrome pregnancies. Most women for whom a prenatal diagnosis of fetal Down syndrome is made, chose to terminate the pregnancy (93%), and this proportion has not changed over the study period. What's already known about this topic? There have been many advances in screening to assess the risk of fetal aneuploidy 39 over the last 30years, with the most recent development being use of cell-free 40 DNA (non-invasive prenatal testing). What does this study add? The availability of prenatal tests for fetal aneuploidy over the last 30years has significantly reduced the live-birth prevalence of Down syndrome in Western Australia. This is despite of an increasing rate of fetal Down syndrome. Without prenatal diagnosis and termination, the rate of live-born infants with Down syndrome would have doubled between 1980 and 2013.