Evaluation of chromosomal abnormalities from preimplantation genetic testing to the reproductive outcomes: a comparison between three different structural rearrangements based on next-generation sequencing.

PURPOSE The aim of this study was to determine factors affecting the chromosome imbalance in blastocysts and reproductive outcomes by a comparison between the reciprocal translocation (REC), inversion (INV), and Robertsonian translocation (ROB) carriers. METHODS Couples with one partner carrying translocation or inversion underwent preimplantation genetic testing for chromosomal structural rearrangement (PGT-SR) cycles, including 215 PGT-SR cycles performed in subsequent 164 frozen-thawed embryo transfer cycles and 61 prenatal diagnoses of fetuses and 59 normal live birth babies. A total of 899 samples were processed by whole-genome amplification followed by next-generation sequencing (NGS). Karyotype and chromosome microarray analyses were used to confirm the PGT results from the amniotic fluid samples. RESULTS A total of 843 blastocysts from 124 REC, 21 INV, and 35 ROB carriers were diagnosed by PGT-SR. The percentage of unbalanced blastocysts was significantly higher in REC than in INV and ROB carriers (64.31% vs. 28.05% vs. 37.02%). Stratification analysis of female carrier age and gonadotropin doses showed no significant increase in unbalanced chromosomal abnormalities in the three groups. Also, the different breakpoints in chromosomal arms did not affect the rate of unbalanced chromosomes in the embryos. Logistic regression indicated blastocyst quality as a statistically significant risk factor associated with unbalanced chromosomal abnormalities from translocation carriers (P < 0.001). The source of abnormalities in the three groups showed significant differences such that the abnormalities in REC mostly originated from parental translocation but the abnormalities in INV were mainly de novo variations. 164 blastocysts were transferred, and there were no significant differences in the clinical pregnancy rate and miscarriage rate. A total of 59 healthy babies were born, and there were no significant differences in the gender ratio and birth height, except the birth weight of boys between INV and ROB groups (P = 0.02). The results of amniocentesis revealed that more fetuses have normal chromosomal karyotypes than balanced carriers, particularly in the REC group. CONCLUSIONS Reciprocal translocation carriers have more risk of unbalanced rearrangement, but embryonic chromosome abnormalities of inversion carriers come mainly from de novo variations. This is the first study specifically comparing three different PGT-SRs using the NGS method and evaluating their reproductive outcomes. Our findings will provide the reciprocal translocation, inversion, and Robertsonian translocation carrier couples with more accurate genetic counseling on the reproductive risk of chromosomal imbalance.