The influence of balanced complex chromosomal rearrangements on preimplantation embryonic development potential and molecular karyotype
Abstract Background: Balanced complex rearrangements (BCCR) are balanced chromosomal structural aberrations that involve two or more chromosomes and at least three breakpoints. It is very rare in the population. The objective is to explore the difference of influence of three types of BCCRs on early embryonic development and embryonic molecular karyotype. Results: Twelve couples were recruited including four couples of three-way rearrangements carriers (group A), three couples of double two-way translocations carriers (group B) and five couples of exceptional CCR carriers (group C). After seventeen preimplantation genetic testing (PGT) cycles, 243 oocytes were retrieved, including 207 mature oocytes, and 181 oocytes normally fertilized after intracytoplasmic sperm injection. The number of embryos forming on day3 in three groups were 87.88%, 97.78% and 77.14%, which was significantly different (P=0.01). Compared with group B, the rate of embryo formation was statistically significantly lower in group C (P=0.01). Furthermore, the rates of high-quality blastocysts in three group were 14.71%, 48.15% and 62.96%, respectively, which was significantly different (P=0.00). Compared with group B and C, the rate of high-quality blastocysts in group A was statistically significantly lower (P=0.00; P=0.00). Comprehensive chromosome analysis was performed on 83 embryos, including 75 trophectoderm cells and 8 blastomeres. Except 7 embryos failed to amplify, 9.01% embryos were diagnosed as euploidy, and 90.91% were diagnosed as abnormal. As for group A, the euploid embryo rate was 10.71% and the abnormal embryo rate was 89.29%. In group B, the euploid embryo rate was 3.85%, the abnormal embryo rate was 96.15%. The euploid embryo rate was 13.04%, the abnormal embryo rate was 86.96% in group C. There were no significant differences among the three groups (P = 0.55). Conclusions: The couples of double two-way translocations carriers have more chance to get balanced or normal embryos probably, and there may be more high-quality blastocysts in exceptional CCRs, but the blastocyst formation rate was similar among the three type of BCCR. Different types of BCCR had little effect on the embryonic molecular karyotype. The difference of influence of BCCR on early embryonic development and molecular karyotype should be further studied.