Objectives: To evaluate the performance of non-invasive prenatal testing (NIPT) for the detection of fetal trisomy 9 in prenatal screening and to investigate the prenatal appearances and genetic counseling of trisomy 9 fetuses.
Materials and methods: The ultrasonography information, laboratory detection and pregnancy outcome of 16 cases of single pregnancy with trisomy 9 identified by NIPT who received amniocentesis in our prenatal diagnosis center from January 2018 to December 2020 were retrospectively analyzed.
Results: Among the 16 cases, 2 cases of trisomy 9, 3 cases of trisomy 9 mosaicism, 2 cases reporting of regions of homozygosity and 9 cases of false positive were diagnosed. Among the true positive cases, 4 cases showed abnormal ultrasonic finding: 3 cases terminated pregnancy and 1 case was lost to follow-up. Another 1 case was in utero fetal demise in the second trimester without structural abnormality, and 2 cases were normal live birth without developmental abnormalities. In the 9 cases with normal kayrotyping, 1 case had termination of pregnancy and 1 case with mental retardation and poor cognitive ability, other 7 had good pregnancy outcomes.
Conclusion: Our results may be helpful for the selection of prenatal diagnostic strategies and genetic counseling for pregnant women with trisomy 9 revealed by NIPT.
Keywords: Chromosome microarray analysis; Mosaicism; Non-invasive prenatal testing; Prenatal diagnosis; Regions of homozygosity; Trisomy 9.
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