Objective:To study the prenatal diagnostic value of the fluorescence in situ hybridization(FISH)in positive cases of noninvasive prenatal testing(NIPT). Methods:The number of fetal 13

18

21

X and Y chromosomes in mniotic fluid samples from 22 of NIPT positive cases was detected by FISH

as well as using G banding karyotypes analysis after cell culture. The consistency between the results of the FISH and karyotypes was compared by means of Kappa test. Results:All samples of the 22 cases were successfully detected by FISH. The results showed 18 cases with fetal aneuploidy

including 2 cases of 13 trisomy

11 cases of 21 trisomy

1 cases of 18 trisomy

1 case of XXY/XY chimeric type

1 case of XXY

1 case of XXXXY and 1 case of XYY and 4 cases with normal number of fetal chromosome. The consistency between the results of FISH and karyotype was extremely strong(Kappa=1). Conclusion:NIPT needs further definite diagnosis due to its false positive result possibility. FISH is a simple

fast and efficient method for early prenatal diagnosis of NIPT positive cases.