Genetic effects of a 13q31.1 microdeletion detected by noninvasive prenatal testing (NIPT)

Microdeletions of chromosome 13q31.1 are relatively rare. These types of deletions may cause different genetic effects on genotypes and/or phenotypes. There are several ways to detect microdeletions; noninvasive prenatal testing (NIPT) is the newest detection method. In this study, we aimed to investigate the genetic effects of a 13q31.1 microdeletion detected by NIPT and to reconfirm the feasibility of this procedure in predicting sub-chromosomal copy number variations (CNVs). The 13q31.1 microdeletion, which has previously been described as a disease-associated fragment, was detected by NIPT in a pregnant woman. To validate the finding and to explain the origin of this sub-chromosomal CNV, we collected fetal amniotic fluid and parental blood samples and tested the samples using array-based comparative genomic hybridization (aCGH). Karyotype analysis was performed on all of the samples to rule out balanced or mosaic anomalies. The aCGH results confirmed the NIPT findings. We detected the same type of microdeletion in the fetus and the mother via aCGH. The mother had a normal phenotype; therefore, in a post-test genetic counseling session, we predicted a normal phenotype for the fetus. After delivery, the normal phenotype of the newborn confirmed our prediction. Based on the present study, this 13q31.1 microdeletion may be considered as a chromosomal polymorphism. This study also reconfirmed the feasibility of obtaining a molecular karyotype of a fetus via NIPT.