Abstract: Objective：To analyze the rate of sex chromosomal mosaicism in our prenatal diagnosis at the second trimester, and the pregnant outcomes of those fetuses with sex chromosomal mosaicism. Methods: The data of prenatal diagnosis by the karyotype analysis of amniotic fluid, from January 2016 to December 2017, were retrospectively analyzed. The pregnant outcomes of 35 fetuses with sex chromosomal mosaicism were then analyzed. Results: The detection rate of sex chromosomal mosaicism was 0.34% (35/10 341), including three types of mosaicism: mos 45,X/46,XX (17); mos 45,X/46,XY (8); 45,X and other abnormal karyotype mosaic (10). In those cases of sex chromosomal mosaicism, the indications of prenatal diagnosis were the numerical abnormality of sex chromosome by NIPT, the high risk by Down screening, abnormal ultrasound and the advanced maternal age, in which their rates of pregnant termination were 86%(12/14), 83%(5/6), 75%(6/8) and 29%(2/7). Conclusions: It is necessary to confirm further the prenatal diagnosis of sex chromosomal mosaicism by CMA, FISH or the cord blood karyotype analysis as well as ultrasound, so as to provide the scientific and effective reference for prenatal genetic counseling.

Key words: Prenatal diagnosis, Sex chromosome aberrations, Mosaicism, Pregnancy outcomes