Analysis of clinical outcomes and meiotic segregation modes following preimplantation genetic testing for structural rearrangements using aCGH/NGS in couples with balanced chromosome rearrangement

Effects of Carrier's sex on the outcome of embryos and pregnancies in 412 couples undergoing preimplantation genetic testing for structural rearrangements

STUDY DESIGN

To ascertain whether the carrier's sex affects the outcome of embryos and pregnancies in couples undergoing preimplantation genetic testing for structural rearrangements (PGT-SR).

METHODS

This retrospective study comprised 412 couples with reciprocal translocations (RecT), Robertsonian translocations (RobT), or inversions (INV) between January 2017 and October 2022. We applied next-generation sequencing (NGS) on 2588 embryos after trophectoderm (TE) biopsy.

RESULTS

Genetically transferable blastocyst rate was higher in the male carrier group (34.0 % vs 31.7 %, P = 0.013) relative to the female carrier group whereas other embryo and pregnancy outcomes remained similar. Further analysis revealed that this result was primarily due to the alteration of segregation patterns in the RobT subgroup, in which the proportion of alternate segregation was higher (84.3 % vs 66.4 %, P < 0.001) in male carriers compared with female carriers. In the RecT subgroup, the genetically transferable blastocyst rate between male and female carriers was similar although the segregation models also changed, such that the frequency of the adjacent-1 segregation pattern was higher in male carriers than in female carriers (42.5 % vs 34.7 %, P = 0.002). In addition, interchromosomal effect (ICE) did not differ between male and female carriers although ICE was lower in male carriers of the RobT subgroup (pure ICE: 35.50 % vs 44.30 %, P = 0.14; total ICE: 35.50 % vs 40.30 %, P = 0.32) and higher in male carriers of the INV subgroup (pure ICE: 42.3 % vs 37.20 %, P = 0.33; total ICE: 40.90 % vs 36.00 %, P = 0.36).

CONCLUSIONS

The carrier's sex was closely associated with the genetically transferable embryo rate in couples undergoing PGT-SR, principally resulted from the change in segregation pattern in the RobT subgroup but not in the RecT and INV subgroups.

Preimplantation genetic testing using comprehensive genomic copy number analysis is beneficial for balanced translocation carriers

Balanced chromosomal translocation is one of chromosomal variations. Carriers of balanced chromosomal translocations have an increased risk of spontaneous miscarriage. To avoid the risk, preimplantation genetic testing (PGT) using comprehensive genomic copy number analysis has been developed. This study aimed to verify whether and how embryos from couples in which one partner is a balanced translocation carrier have a higher ratio of chromosomal abnormalities. A total of 894 biopsied trophectoderms (TEs) were obtained from 130 couples in which one partner was a balanced translocation carrier (Robertsonian translocation, reciprocal translocation, or intrachromosomal inversion) and grouped as PGT-SR. Conversely, 3269 TEs from 697 couples who experienced recurrent implantation failure or recurrent pregnancy loss were included in the PGT-A group. The transferable blastocyst ratio was significantly lower in the PGT-SR group, even when bias related to the sample number and patient age was corrected. Subgroup analysis of the PGT-SR group revealed that the transferable blastocyst ratio was higher in the Robertsonian translocation group. Because the PGT-SR group had a higher proportion of untransferable embryos than the PGT-A group, PGT using comprehensive genomic copy number analysis was more beneficial for balanced translocation carriers than for infertility patients without chromosomal translocations. The frequencies of de novo aneuploidies were further analyzed, and the frequency in the PGT-SR group was lower than that in the PGT-A group. Therefore, we could not confirm the existence of interchromosomal effects in this study.

Preimplantation genetic testing: A remarkable history of pioneering, technical challenges, innovations, and ethical considerations

Preimplantation genetic testing (PGT) has emerged as a powerful companion to assisted reproduction technologies. The origins and history of PGT are reviewed here, along with descriptions of advances in molecular assays and sampling methods, their capabilities, and their applications in preventing genetic diseases and enhancing pregnancy outcomes. Additionally, the potential for increasing accuracy and genome coverage is considered, as well as some of the emerging ethical and legislative considerations related to the expanding capabilities of PGT.