Derivative and non-derivative aneuploidy rates in PGT tested blastocysts from carriers of structural rearrangements

Research question: What is the likelihood of having an euploid embryo when undergoing preimplantation genetic testing for structural rearrangements (PGT-SR)? Design: PGT-SR data from 364 couples (2822 trophectoderm biopsies) with a reciprocal translocation (RecT, n = 263), Robertsonian translocation (RobT, n = 79) or inversion (Inv, n = 22) were analysed retrospectively. Rates of euploid, derivative aneuploid or non-derivative aneuploid were evaluated for each cycle, stratified by the type of rearrangement and parent of origin. Results: Inv had the highest rate of euploid embryos (47.0–52.5%), followed by RobT (34.1–45.2%) and RecT (24.0–28.2%). The rates of euploid embryos were significantly lower for carriers of RobT and RecT compared with age-matched controls (57.6–59.0%). Maternal versus paternal rearrangements had significantly higher rates of derivative-abnormal findings for RobT (41.6% versus 20.2%) and RecT (60.2% versus 52.7%). Aneuploidies involving other chromosomes did not differ significantly in frequency between rearrangement carriers (38.1–41.9%) and age-matched controls (40.6–42.4%). Conclusions: Data from this study demonstrated that Inv carriers have the highest rates of euploid embryos among all carriers of chromosomal rearrangements, that maternal rearrangements confer a higher risk of abnormal embryos, and that evidence for an interchromosomal effect on aneuploidy rates was not present in this cohort. This analysis of over 2700 PGT-SR biopsies enabled generation of likelihood-of-transfer tables stratified by type of translocation, parent of origin, and number of biopsies, which can be used to help counsel patients pursuing PGT-SR.