Abstract:

Objective To analyze the genetic analysis results and pregnancy outcome follow-up results of 11 fetuses with chromosome 12 copy number variation（CNV）. Methods From January 2017 to December 2023，6 002 pregnant women who underwent interventional prenatal diagnosis [chromosome karyotype analysis and single nucleotide polymorphism array（SNP-array）] at Quanzhou Women's and Children's Hospital were enrolled. Among them，11 pregnant women with fetal chromosome 12 abnormalities were determined. Among them，case 2 fetus was verified by fluorescence in situ hybridization（FISH）. Results The prenatal diagnosis karyotype result of case 1 fetus was 46，XN，der（1）t（1；12）（p36.3；q24.1），that of case 2 fetus was 47，XN，+dic（12）（q12）[3]/46，XN[97]，and that of case 3 fetus was 47，XN，+i（12）（p10）. Case 4 fetus had failed amniotic fluid culture. Case 5-case 11 fetuses had no obvious abnormalities in karyotype. Case 1 fetus had 19.6 Mb duplication and 1.7 Mb deletion in the chromosome 12 12q24.13q24.33 and chromosome 1 1p36.33p36.32，case 2 fetus had 40.2 Mb tetrasomic duplication in the chromosome 12 12p13.33q12，case 3 fetus had 34.6 Mb tetrasomic duplication in the chromosome 12 12p13.33p11.1，and the chromosome CNV of case 1-case 3 fetuses were all pathogenic CNV. Case 4 fetus had 2.2 Mb duplication in the chromosome 12 12p13.31，which was a possible pathogenic CNV. Case 5-case 11 fetuses had 327.7 kb-1.0 Mb CNV in the chromosome 12，all of which were of unknown clinical significance. Case 1，case 4，case 6-case 10 fetuses were inherited from phenotypically normal parents，case 2，case 3，case 5 fetuses had CNV as new mutations，and case 11 fetus was not verified. Case 2 fetus had approximately 82% of cells during division as tetrasomic cells at the 12pter probe site fragment. Case 1-case 4 fetuses' pregnant women terminated the pregnancy；case 5，case 7，case 10，case 11 fetuses' pregnant women continued the pregnancy，and the newborns were healthy after birth；case 6，case 8 fetuses' pregnant women continued the pregnancy，and the newborns showed abnormalities after birth，received medical intervention，and are currently healthy；case 9 fetus' pregnant woman continued the pregnancy，and the fetus was lost to follow-up after birth. Conclusions The use of multiple different determination techniques in prenatal diagnosis can increase the determination rate of chromosome abnormalities，clarify the specific situation of CNV，assist in pathogenicity interpretation，evaluate prognosis，and guide pregnancy.

Key words: Copy number variation, Chromosome 12, Single nucleotide polymorphism array, Tetrasomy