OC05.08: Prenatal screening and testing for 45,X: lessons learned from 18,299 cfDNA results from the SMART study.

Seven cases of 45,X were confirmed in the cohort including 4 with mosaicism, for a prevalence of 1:2614. cfDNA identified 6/7 cases (sensitivity=85.7%). cfDNA results reported high risk for 45,X in 24 cases; 6 of these were confirmed (PPV=25.0%). CfDNA screening for 45,X can be complicated by mosaicism and the diagnosis may be delayed due to variable and late onset of manifestations. We aimed to define the prevalence and screening performance for 45,X using single nucleotide polymorphism (SNP) - based cfDNA screening for aneuploidy and 22q11.2DS, in a large prospective registry study with genetic confirmation (SMART registry study). [Extracted from the article]