Embryonic Chromosomal Changes and Embryonic Morphology: What Is Their Relationship to the Choice of the Best Embryo

Abstract

OBJECTIVE:The embryonic morphology is an important factor while evaluating embryonic potential. With the advances in the field of genetic analysis techniques, it is known that the decision to transfer an euploid embryo is related to higher pregnancy rates. However, genetic evaluation is an invasive exam, which does not occur with the morphology evaluation, which can be considered an advantage. Nonetheless, it is not yet known whether it is possible to associate embryonic quality with euploidy, and the literature are very controversial. Because of this, we aimed to evaluate the effects of embryo quality on the aneuploidy.DESIGN: Prospective study. MATERIALS AND METHODS: Data from 1037 blastocysts were collected that were cultivated in continuous culture medium in incubators at 37oC, CO 2 8%, and O 2 5%. The blastocyst morphology was classified by SART criteria and the best quality embryos (3-6; A and B) were denominated top-quality embryos. The blastocysts were biopsied, and the cells were sending to PGT-A, subsequently being cryopreserved. According to the results, the embryos were separated into three groups: >75% aneuploidy (G1), between 74,9%-24,9% aneuploidy (G2), and <25% aneuploidy (G3). 320 couples undergoing in vitro fertilization in 2019 agreed to participate in the study. The female partners underwent controlled ovarian stimulation and had their oocytes recovered and subsequently inseminated. The fertilized embryos were cultivated in the group with the CSCM (Irvine) culture medium. In the stage of the blastocyst, they were biopsied and the preimplantation genetic diagnosis was performed by next-generation sequencing. Besides that, the embryos were evaluated for their quality through the morphological assessment.RESULTS: Considering the morphologic variables, the G3 group (<25% aneuploidy) presented a significant (p<0.01) higher rate of top-quality embryos (55.1%AE39.1%) when compared with the G1 group (35.9%AE 41.9%). No significant difference was found when compared to the G3 group with the G2 group (46.4%AE40.0%), and the G2 group with the G1 group, concerning the rate of top-quality embryos. These results show that embryos with better morphology assessment end up being euploid, which would allow the association of morphology evaluation with the embryo genetics status. However, this study has the same weakness that other blastocysts morphological studies, the evaluation always can be influenced by the observer, in addition to the possible loss of events due to time of analysis.CONCLUSIONS: Because of this, further studies are necessary to establish whether it is safe to predict ploidy through embryo morphological analysis, also with the support of new technologies such as time-lapse. However, this study shows the relation between blastocyst aneuploidy and embryo quality on day 5/6. Our results are close to the routine of the vast majority of laboratories in the world, which do not have the resources of time-lapse technology, and It is possible to think of a joint strategy that allows the association o...