Clinical value of different genetic testing methods for detection of true fetal chromosome mosaicism / 中华围产医学杂志

ABSTRACT

Objective:To investigate the performance of chromosome karyotype, chromosomal microarray analysis (CMA) and fluorescence in situ hybridization (FISH) in prenatal diagnosis of true fetal chromosome mosaicism. Methods:This retrospective study enrolled 40 women with true fetal chromosome mosaicism from 4 071 singleton pregnant women who were indicated for and underwent amniocentesis or/and cordocentesis in the the First Affiliated Hospital of Sun Yat-sen University from April 2018 to August 2021. The results of chromosome karyotyping, CMA and FISH, the types of chromosomal mosaicism, mosaicism ratio and pregnancy outcomes were analyzed using Chi-square test. Results:(1) The detection rate of true fetal mosaicism was 0.98% (40/4 071). (2) Sex chromosome mosaicism accounted for 42.5% (17/40). Other chromosomal mosaicism involved chromosomes 21, 22, 18, 16, 7, 12, 15, 17 and 20, as well as balanced chromosomal translocation. (3) The detection rate of true fetal mosaicism by chromosome karyotyping was 77.4% (24/31) from amniotic fluid samples and 10/19 from umbilical cord blood samples, while that data by CMA was 76.7% (23/30) and 7/11,respectively. (4) Of the 40 pregnant women with fetal chromosome mosaicism, FISH test was performed on 20 cases (14 cases were verified with both amniotic fluid and umbilical cord blood samples, five with amniotic fluid samples and one with umbilical cord blood sample), and all of the diagnosis of mosaicism were confirmed. For those with mosaicism ratio <30%, the detection rate by FISH was higher than that by CMA among amniotic fluid samples [14/19 vs 43.5% (10/23), χ2=3.88, P=0.049]. (5) Among the 40 pregnant women, five were lost to follow-up; 18 chose to terminate the pregnancy; and 17 continued the pregnancy to delivery. No abnormalities in mental or physical development were reported in the 17 neonates after birth or during on-line follow-up between 6 to 24 months old. Of the 14 pregnant women with mosaicism ratio <30% which confirmed by FISH, eight chose to continue the pregnancy, and no abnormalities in mental development or growth were found in the neonates. Conclusions:In prenatal diagnosis of true fetal choromosome mosaicism, the incidence of sex chromosome mosaicism is the highest. FISH may improve the prenatal diagnosis rate of mosaicism and is more accurate in determining the mosaicism ratio. The combination of FISH, CMA and chromosome karyotyping would significantly improve the detection rate of chromosomal mosaicism and assess the mosaicism ratio more accurately, which is of great value in clinical consultation and evaluation of fetal prognosis.