Detection of fetal subchromosomal aberration with cell-free DNA screening led to diagnosis of parental translocation: Review of 11344 consecutive cases in a university hospital.

BACKGROUND: Fetal chromosome aberrations and sub-chromosomal copy number variations (CNVs) are not rare. There are several ways to detect duplications and deletions; cell-free DNA screening (cfDNA screening) is nowadays an accurate and safe detection method. The objective of this study is to report the feasibility of cfDNA screening as an indicator of parental balanced chromosome translocation. RESULTS: From February 2015 to March 2016, cfDNA screening was offered to 11344 pregnant women. 137 out of 11344 individuals tested positive for aneuploidies using cfDNA screening were confirmed by karyotyping. 6 additional cases also tested positive for other deletion/duplication were confirmed by chromosomal microarray analysis (CMA). 11201 patients tested negative and 10342 of them were confirmed through interviews after delivery. Among the 137 cases that were screened positive in cfDNA screening, 91 were common trisomies (63 cases of trisomy 21, 25 cases of trisomy 18 and 3 cases of trisomy 13) and 46 cases were positive for sex-chromosomal abnormalities. In addition, 6 cases were positive for other deletion/duplication in which 2 were identified as terminal duplication and deletion on different chromosomes. The cfDNA screening findings were confirmed by CMA or karyotyping, and the origins of CNVs were validated afterward by karyotyping or fluorescence in situ hybridization (FISH) using parental blood samples. CONCLUSION: CfDNA screening may help identify deletions and duplications in fetus, which in some cases may indicate risk of a parent being a balanced rearrangement carrier, and that the diagnostic follow-up testing is necessary.

A feasible diagnostic approach for the translocation carrier from the indication of products of conception.

BACKGROUND: Chromosome translocations are rare but frequently associated with infertility. The objective of this study is to investigate the feasibility of using chromosomal microarray analysis (CMA) on products of conception (POC) samples as an indicator of parental balanced translocation. From January 2011 to December 2016, CMA using Affymetrix Cytoscan™750K array was performed on 1294 POC samples in our hospital. Karyotyping and fluorescence in situ hybridization (FISH) using parental blood samples were performed to validate the origin of subchromosomal copy number variations (CNVs). RESULTS: In the 1294 cases of POCs, we detected CNVs of terminal duplication and deletion that imply unbalanced translocation derivatives in 16 cases, and accurate diagnosis with the parental study was made in all the cases by karyotyping and/or FISH. In 10/16 (62.5%) of these cases, CNVs were inherited from one carrier parent of balanced translocation (Cases 1 to 10), while 6/16 (37.5%) cases occurred de novo (Cases 11 to 16). CONCLUSION: This study clearly illustrated the importance of the utilization of CMA on POC, followed by parental karyotyping and FISH to better characterize CNVs. This approach is especially useful for couples in whom one partner carries a cryptic/submicroscopic balanced translocation but has an apparently normal karyotype.