Dados do Trabalho

Title

Correlation between embryo’s morphological evaluation, euploidy and implantation rate

Objective

The aim of this study was to determine the relationship between morphological parameters and the incidence of chromosomal abnormalities and to evaluate the potential for implantation of euploid embryos.


Methods

This is a retrospective observational study based on the analysis of medical records from 96 patients who underwent in vitro fertilization (IVF) cycles, totaling 323 biopsied blastocysts. Data were collected from a private Assisted Reproduction clinic in Belo Horizonte. Embryonic morphology assessment was performed according to the Gardner and Schoolcraft system, wherein the inner cell mass (ICM) and trophectoderm (TE) cells were scored based on their number and cohesion into three different grades (A, B, C), with A representing the highest grade. Finally, the incidence of euploid and aneuploid cells in trophectoderm biopsies was compared with embryonic morphological quality and pregnancy rate.


Results

The rate of euploidy was significantly higher in embryos with faster growth, with 41.92% of embryos reaching the blastocyst stage on the fifth day being euploid, compared to 22.58% on the sixth day of culture. 

Regarding morphological grades, the rate of aneuploidy increased significantly in embryos with poorer ICM evaluations, as the euploidy rate was 42.57%, 35.2%, and 23.07% for grades A, B, and C, respectively. As for the TE, the euploidy rates for embryos with grades A and B were comparable, with euploidy rates of 39.28% and 41.29%, respectively. These values were higher than the euploidy rate found in embryos with TE grade C, which showed a rate of only 28.57%.

Regarding the potential for implantation of euploid embryos, only 34% of cases resulted in a clinical pregnancy, compared to 63% of cases where no pregnancy occurred. Additionally, a 2% rate of ectopic pregnancy was observed. Despite different morphologies, the pregnancy rates were similar for embryos classified with grade A and B ICM (50%). However, when evaluating the TE, embryos classified as grade A had a clinical pregnancy rate of 30%, compared to a rate of 60% for embryos classified with grade B and 10% for grade C embryos.



Conclusion

The selection of embryos with the highest potential for implantation remains one of the most significant challenges in assisted reproduction. Several studies have demonstrated a positive correlation between embryonic morphological appearance and clinical outcomes, suggesting that better morphological aspects may lead to improved chances of successful implantation. However, the complex relationship between embryonic morphology and chromosomal constitution has led to the introduction of preimplantation genetic testing as a complementary tool aimed at selecting euploid embryos and enhancing the delivery rate per transfer.

This study confirmed a moderate association between euploidy and blastocyst morphological characteristics. An increased rate of aneuploidy was observed among blastocysts with poorer morphological scores, while embryos with better scores showed a higher likelihood of euploidy. Thus, selection based on morphology appears to be an acceptable parameter for increasing the probability of transferring chromosomally normal embryos. However, it is important to note that this methodology still presents discrepancies in results, with euploid embryos having poor scores and vice versa. For this reason, selection based on embryonic morphology cannot be used as an alternative to genetic testing to minimize the risk of transferring chromosomally abnormal embryos.

Through the results, it was also possible to investigate the role of morphological evaluation in predicting the chance of successful implantation, excluding chromosomal abnormalities from the analysis as a confounding factor. And the morphology appears not to be an important parameter to consider which euploid embryos should be transfer, since better outcomes were observed in embryos with lower quality trophectoderm. Also, euploid embryos with poorer quality ICM produced the same implantation rate as morphologically better evaluated blastocysts.

Keywords

embryos, euploidy, morphology, implantation rate