Confined placental mosaicism: implications for fetal chromosomal analysis using microarray comparative genomic hybridization

Chromosomal microarray analysis on uncultured chorionic villus sampling can be complicated by confined placental mosaicism for aneuploidy and microdeletions

“…One report describes a case of a mosaic microdeletion (979 kb at bands 2p23.1p22.3, CPM type I), which was identified among 464 cytogenetically normal prenatal samples . In another case, an exonic deletion of the STS gene on Xp22.31 was reported to be CPM type I . In a third case, a mosaic 22q11.2 deletion was detected through NIPS, which was subsequently found to be present in two out of three placental biopsy sites, while absent from maternal and postnatal neonatal peripheral blood samples …”

“…Overall, 0.36% of CVS samples analyzed demonstrated submicroscopic or nearly submicroscopic CNVs findings (5 out of 1382, including provisional CPM I cases). These data suggest that, in addition to mosaic aneuploidy, mosaic submicroscopic CNVs detected by CMA on direct intact CVS should also be interpreted carefully, and confirmation on a different sample type, preferentially on amniocytes, may be warranted …”

Confined placental mosaicism for 22q11.2 deletion as the etiology for discordant positive NIPT results

“…Both microarray and MLPA analysis of the cultured sample from the CVS, the newborn and parental peripheral blood studies did not detect the microdeletion. Placental samples were not studied …”

Cytogenetic confirmation of a positive NIPT result: evidence-based choice between chorionic villus sampling and amniocentesis depending on chromosome aberration

“…However, despite the phenomenon of CPM, some of them use DNA from the whole chorionic villus, which is a mixture of cytotrophoblast and mesenchymal core, which leads to problems with interpretation of mosaic results [24]. In order to avoid uncertain results, it is important to separate cytotrophoblast from the mesenchymal core and use the DNA from both cell lineages separately [25] or at least that of the mesenchymal core in accordance with the European cytogenetic guidelines [26].…”