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.