Performance of conventional cytogenetic analysis on chorionic villi when only one cell layer, cytotrophoblast or mesenchyme alone, is analyzed.

OBJECTIVE: To provide an estimation of the probability of error when chorionic villi (CV) cytogenetic analysis is limited to a single placental layer; either a direct preparation (Dir) or long-term culture (LTC). METHODS: We retrospectively reviewed cytogenetic studies on 81,593 consecutive CV samples in which both Dir and LTC were analyzed. All mosaic cases received amniocentesis. The false omission and false discovery rates were calculated by assessing the results that would have been reported when analysis was limited to either Dir or LTC. RESULTS: For all abnormalities combined, the proportion of normal Dir or LTC only reports that would have been inconsistent with a subsequent amniocentesis was 0.09% and 0.03%, respectively (false omissions). Among abnormal reports based on Dir or LTC alone, 8.01% and 3.17%, respectively, would be inconsistent with a subsequent amniocentesis result (false discoveries). Differences are present for individual abnormalities. CONCLUSIONS: From the perspective of identifying all abnormalities of potential clinical significance, the analysis of both placental layers is optimal. LTC alone is the preferred approach if only one layer of placenta is to be analyzed. Although rare, it is important to acknowledge that one cell layer analysis alone can cause misdiagnosis due to undetected mosaicism.

An evidence-based scoring system for prioritizing mosaic aneuploid embryos following preimplantation genetic screening.

The aim of this study was to devise an evidence-based scoring system for prioritizing mosaic aneuploid embryos for transfer. A retrospective analysis was performed of all sequential cytogenetic and molecular results on chorionic villi samples (n = 72,472) and products of conception (n = 3806) analysed at a single centre. The likelihood that a mosaic aneuploidy detected in chorionic villi samples will involve the fetus, the incidence of clinically significant fetal uniparental disomy in the presence of a mosaic in chorionic villi and the chance of the mosaicism culminating in miscarriage were used to generate a scoring system for prioritizing mosaic aneuploid embryos detected by preimplantation genetic screening. A composite score was obtained for each individual mosaic aneuploidy after assignment of an individual risk score based on the incidence/likelihood of each adverse outcome. A final additional score was assigned to viable full or mosaic aneuploidies with a well-defined phenotype. The higher the composite score the lower the priority for embryo transfer. In conclusion, due to the paucity of prospective studies on the actual transfer of mosaic aneuploid embryos, we suggest using this evidence-based scoring system to provide a useful tool for clinicians, embryologists and patients.