[Prenatal genetic diagnosis of a partial 21 trisomy fetus with nasal bone dysplasia].

To explore the nature of chromosomal abnormality in a fetus with nasal bone dysplasia and clarify its clinical effect.Fetal chromosome karyotype was analyzed by G-banding. Single nucleotide polymorphism array (SNP-array) was used to detect the chromosomal copy number variations, and fluorescence in situ hybridization (FISH) was used to verify the result.Fetal karyotype analysis showed an unknown chromosomal fragment in 21q21 region. SNP-array discovered a 7.5 Mb duplication in the 21q22.12q22.3 region. FISH confirmed that the unknown fragment was derived from a 21q22.12q22.3 duplication.Combined use of karyotype analysis, SNP-array and FISH has clarified the nature of chromosomal abnormality in a fetus with nasal bone dysplasia, which has enabled more accurate prenatal diagnosis and genetic counseling.