Abnormal chromosomes identification using chromosomal microarray.

In this study, we presented a case series to highlight the chromosomal microarray (CMA) in identifying chromosomal abnormalities which is undetectable by conventional karyotyping or known abnormal chromosomes without clear diagnosis. Extensive studies showed that CMA was gradually accepted as a prenatal invasive testing during pregnancy. The aim of this study was to evaluate the diagnostic effect of CMA for foetuses with abnormal chromosomes unrecognised by conventional karyotyping. Pregnant women who need prenatal diagnosis with all indications were enrolled in this study. For aberrant cytogenetic findings that cannot be defined by routine karyotyping, single nucleotide polymorphism array (SNP-array) was used. Six cases with abnormal karyotype were included in the study. With higher resolution of translocation breakpoints, CMA could detect smaller chromosomal imbalances that were undetectable by karyotyping. This study highlights the value of CMA for the detection of submicroscopic abnormalities in foetuses that cannot be detected by conventional karyotyping. Impact Statement Chromosomal microarray (CMA) offers additional diagnostic benefits by revealing submicroscopic imbalances or copy number variations (CNVs) that are too small to be identified on a standard G-banded chromosome preparation. We added a case series to highlight the CMA in identifying chromosomal abnormalities not detectable by conventional karyotyping or known abnormal chromosomes without clear diagnosis. This study highlights the value of CMA in the case of associated foetuses with submicroscopic abnormalities that cannot detect by conventional karyotyping.