Abstract: Objective: To explore the application of fluorescence in situ hybridization (FISH) in the prenatal diagnosis of chromosomal mosaicism. Methods：A total of 22 cases of potential chromosome mosaicism detected by the villus/aminotic cell G-band karyotype analysis were included in this study. The abnormities of chromosome karyotype and the ratio of chromosome mosaicism were further analyzed by chromosomal microarray analaysis (CMA) and FISH. Results：In those 22 cases, there were 13 cases of sex chromosome mosaicism, 6 cases of autosomal trisomy mosaicism and 3 cases of sex chromosome structure mosaicism. Almost 50% of chromosomal mosaicism were not found by CMA, which may be related to the fact that CMA can only detect the change of gene copy number and can not detect low ratio of chromosomal mosaicism. Because of great influence on the growth and development of fetus, cases of autosomal trisomy mosaicism were terminated except one case. Three cases of sex chromosome structure mosaicism were confirmed as the dicentric sex chromosome by the combined G-band, CMA and FISH. Conclusions：Multiple methods should be combined to verify the chromosomal mosaicism in those patients with the suspicious chromosomal mosaicism detected by the villus/aminotic cell G-band karyotype analysis in prenatal diagnosis. The combined application of CMA, FISH and G-band, as well as detailed ultrasound evaluation, is required. The accurate diagnosis of the chromosome mosaicism type and the ratio of abnormal mosaicism karyotype can provide a more reliable basis for genetic counseling.

Key words: In situ hybridization, fluorescence；Microchip analytical procedures；Microarray analysis；, Chromosome aberrations；, Mosaicism；, Prenatal diagnosis