P-534 Toward enhanced genetic counseling with PGT-SR: exploring the impact of chromosomal rearrangement type and carrier gender on the acquisition of transferable embryos

Abstract Study question Do chromosomal rearrangement type and gender of carriers influence the ability to obtain transferable embryos? Summary answer Carriers of a reciprocal translocation, particularly female carriers, could have a higher risk of having non-transferable embryos. What is known already Chromosomal translocations are common structural rearrangements in the general population, occurring even 10 times more frequently in the infertile population, as carriers may produce unbalanced chromosomal gametes. Preimplantation Genetic Testing for Structural Rearrangements (PGT-SR) is a crucial tool for selecting embryos to transfer. There are numerous factors that can affect the availability of transferable embryos, and some of the less studied ones are the gender of the carrier and the type of chromosomal rearrangement. Study design, size, duration This is a single-center retrospective study performed between 2016 and 2023, that included 265 biopsies. Embryos were classified as transferable (n = 80, 30%) if they were euploid/balanced or exhibited low-grade mosaicism (< 50%) without the involvement of chromosomes 13, 14, 16, 18, 21, and X. Non-transferable embryos (n = 185, 70%) included those that were unbalanced, aneuploid, or displayed high-grade mosaicism. Differences between groups were assessed using Chi-square and Fisher’s exact tests. Values with p < 0.05* were deemed significant. Participants/materials, setting, methods NGS-based PGT-SR was performed on 265 embryos from 71 cycles of 47 couples. Couples were divided into Robertsonian translocation carrier group (ROB-T, 105 embryos) and Reciprocal translocation carrier group (REC-T, 160 embryos). Subsequently, data was categorized by maternal age: ≤37 (ROB-T=91, REC-T=122) and >37 years (ROB-T=14, REC-T=38), as well as by the gender of the carrier: male carrier group (MC) (ROB-T=77, REC-T=97) and female carrier group (FC) (ROB-T=29, REC-T=74). Main results and the role of chance Of the embryos belonging to ROB-T group, 45/105 (43%) were transferable, while in the REC-T group only 35/160 (22%) were transferable. This difference was statistically significant (p = 0.0004612). It was assessed whether these differences were attributable to maternal age or gender of carriers. In the ≤37, 43% (39/91) of the ROB-T embryos were transferable, but only 25% (30/122) were transferable in the REC-T group (p = 0.007583). In the >37, 43% (6/14) of the ROB-T embryos were transferable versus 13% (5/38) in the REC-T group (p = 0.04951). In both age groups, the obtaining transferable embryos were influenced by the type of translocation. In the MC group, 47% (36/76) of the ROB-T embryos were transferable and only 24% (22/90) were transferable in the REC-T group (p = 0.003467). In the FC group, 31% (9/29) of the ROB-T embryos and 19% (13/70) of the REC-T embryos were transferable (p = 0.2749). In the MC group, the obtaining transferable embryos were influenced by the type of translocation. However, within the FC group, no significant differences were observed. When evaluating non-transferable embryos (185), 71% were unbalanced and 29% were balanced ones with aneuploidies. Unbalanced embryos were more frequent in REC-T carriers in all analyzed groups. Limitations, reasons for caution This study is limited by its retrospective nature and its small sample size. Additionally, it is worth noting the difference in sample size between groups when segmenting the data by maternal age. Wider implications of the findings Our results indicate that the type of rearrangement is relevant in obtaining transferable embryos. Carriers of REC-T, especially female carriers, could have a higher risk of having non-transferable embryos compared to carriers of ROB-T. These findings could be significant for genetic counseling of individuals carrying chromosomal translocations. Trial registration number Not applicable