Abstract:

Objective To explore the value of improved synchronized G⁃banding and chromosomal micro⁃ array analysis（CMA）in prenatal diagnosis of umbilical cord blood. Methods A total of 202 pregnant women who had prenatal diagnosis indications and missed prenatal diagnosis of villus and amniotic fluid in the Eugenic Genetics Department of our hospital from January 2020 to April 2021 were selected. Cord blood samples were collected for the analysis with conventional method and improved synchronous G⁃banding karyotype analysis. At the same time， CMA was used to detect the whole genome copy number variant（CNV）of cord blood DNA. The resolution of G ⁃ banding karyotype and detection rate of abnormality through CMA，synchronized G ⁃ banding and conventional method were compared. Results The resolution of improved synchronous G⁃banding pattern was 500~550 bands， and that of conventional G⁃banding pattern only 320~400 bands. The detection rate of chromosome abnormality of conventional method，improved synchronized G ⁃banding and CMA was 3.47%，4.46% and 9.90%，respectively. Among the 16 CNVs detected by CMA，only 2 microdeletions greater than 5Mb were detected by modified synchro⁃ nized G⁃banding. In addition，there were 3 cases with abnormal karyotype，but normal by CMA. There was signifi⁃ cant difference in the detection rate of chromosome abnormality between improved synchronized G-banding and CMA（χ 2=4.495，P = 0.034）. Conclusion The karyotype resolution of improved synchronized chromosome G⁃banding can be increased to 500~550 bands，which is conducive to detecting more chromosome structural abnor⁃ malities. Together with improved synchronized G⁃banding and CMA，we can improve the detection rate of chromo⁃ some abnormalities，and reduce the birth defects of newborns.

Key words:

improved synchronized chromosome technique, G?banding, chromosomal microarray anal? ysis, cord blood, prenatal diagnosis