EP18.47: Reconfirm prenatal 22q11.2 duplication syndrome with different non‐invasive prenatal testing method: a two‐case study

This study was to perform the prenatal diagnosis of two fetuses with 22q11.2 duplication diagnosed after amniocentesis; each fetus was diagnosed through karyotype analysis and single-nucleotide polymorphism array (SNP-array. W also confirm parents' copy number variation via peripheral blood analysis. Both fetuses were confirm to be de novo 22q11.2 duplications; case 1 and case 2 showed 1.35Mb and 2.94Mb duplications in the 22q11.2 regions respectively. However, we performed SNP-based non-invasive prenatal testing(NIPT) and counting method-based expanded NIPT to see whether 22q11.2 duplications could be detected. The result showed that SNP-based NIPT reported case 1 with low risk for 22q11.2 deletion and they did not report 22q11.2 duplications due to the experiment method. In contrast, case 2 were performed with expanded NIPT and reported with low risk for 22q11.2 deletion and high risk for 22q11.2 duplications (at least 2Mb duplication). Although SNP-based NIPT have an advantage over counting method-based NIPT due to SNP-based NIPT less dependent on the fetal fraction and with lower false-negative and false-positive rates, the clinical importance of expanded NIPT in the early detection of fetal subchromosomal microdeletion and microduplication need to be taken seriously.