Non-invasive prenatal testing detects duplication abnormalities of fetal chromosome 12

The 12q terminal duplication is a chromosomal structural abnormality that has been rarely reported. The common clinical manifestations include intellectual disability and speech delay. We report two cases of patients with a duplication of chromosome 12q which was discovered incidentally during non-invasive prenatal genetic testing (NIPT).

Next generation sequencing-based NIPT and karyotype analysis confirmed the type and inheritance of the rearrangement, and chromosomal microarray-based analysis also confirmed the end replication.

One patient had a 18Mb 12q24.21q24.33 duplication. The other patient had a12.04Mb12.q24.31q24.33 duplication and a 9.56Mb deletion in 18p11.32p11.22. The duplicated regions on chromosome 12 and the deletion on chromosome 18 in the patients were pathogenic, and the fetuses may have clinical characteristics, such as mental retardation, facial deformities, and psychomotor retardation. Ultimately, both pregnant women chose to terminate their pregnancy.

The cases we reported show that NIPT cannot only detect conventional chromosomes, but can also detect microdeletions and microduplications, which broadens the scope of clinical application for NIPT and provides genetic information for high-risk pregnant women as early as possible.