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

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.