The Karyotype Analysis of Sex Chromosome Mosaicism in Prenatal Diagnosis and Their Clinical Outcomes

Abstract Objective To analyze the karyotype of sex chromosome mosaicism in our prenatal diagnosis of 14034 pregnant women in their second trimester, and report the rate of sex chromosome mosaicism and their clinical outcomes.Methods A retrospective analysis of cytogenetic studies of 14043 cases of pregnant women from the Genetic Counseling Clinic from May 2017 to January 2020 by amniocentesis, were performed. Results A total of 46 cases of sex chromosome mosaicism were found, and the sex chromosome mosaicism rate was 0.328%, mainly including four types of mosaicism: mos45,X/46,XX(12); mos45,X/46,XY (11); mos47XXX(or XXY or XYY)/46XX(or XY)(11); and other types of complex abnormal karyotype mosaic(12). Among the 46 fetuses with sex chromosome mosaicism, the indications of prenatal diagnosis includes the numerical abnormality of sex chromosome by NIPT(23/46)，the high risk of trisomy 21 by serum screening(12/46)，abnomal ultrosound(4/46), the advanced maternal age(age ≥35)(4/46), and the histories of abnormal pregnancy(3/46). According to the results of cytogenetic analysis and genetic counseling, the pregnant women would decide to continue or terminate their pregnancy. Conclusion Prenatal cytogenetic diagnosis by amniocentesis is an accurate and convenient method and helps to avoid the delivery of fetuses with chromosomal diseases and reduce the risk of fetal malformation.