Dados do Trabalho

Title

Is embryo morphology at day 3 or at the day of biopsy an important point to pay attention in PGT-A cycles?

Objective

Every blastocyst could be biopsied, but that does not mean that they all should. Discussions about the decision point about performing or not a biopsy in certain embryos is still up for debate, and there is not a consensus among countries, clinics, and even among physicians and embryologists of the same practice. The objective of this retrospective case-control study was to analyze the morphology of embryos at day 3 and on biopsy day, and compare these observations between euploids and aneuploids blastocysts.

Methods

For this study, 125 cycles of IVF and PGT-A were enrolled, analyzing a total of 458 blastocysts. Two groups were defined depending on embryo ploidy: euploid group, with 163 blastocyst, and aneuploid group with 295 embryos. With the purpose of understanding the impact of morphology and days of culture, and to evaluate the possibility of a ploidy prediction at different stages of embryos, the development and morphology of these embryos were assessed at day 3, 5, 6 and 7 or until the biopsy was performed. For day 3 embryos, the quality was determined by using a grade classification where grade 1 (G1) contemplated embryos with 8 cells, < 10% of fragmentation, symmetric cells and without multinucleation; grade 2 (G2) was composed by embryos with 6-7 or 9-10 cells, 10-25% of fragmentation, asymmetric cells and without multinucleation; and grade 3 (G3) contemplated embryos with < 6 or > 10 cells, > 25% fragmentation and asymmetric and multinucleate cells. The day of biopsy, as well as trophectoderm and ICM morphology, were assessed following Gardner classification. Blastocysts were split regarding morphology; good quality embryo (embryos with grade A and/or B) and poor-quality embryos (when ICM or trophectoderm received a grade C). Data were compared using Chi square and Fisher’s exact test with p value ≤ 0.05 considered significant.

Results

On day 3 of culture, for the euploid group (n= 163 embryos), 42.94% embryos were classified as G1, 45.40% were G2 and 11.66% were G3. Among aneuploid embryos (n=295 embryos), 39.66% were in G1, 45.42% in G2 and 14.92% in G3. No alterations were detected on day 3 embryos regarding their morphology and ploidy. As expected, most biopsies were performed on day 6 (76.07% and 77.97% in euploid and aneuploid groups, respectively), in comparison to day 5 (19.63% and 14.58% in euploid and aneuploid group, respectively) and day 7 (4.29% of euploid embryos and 7.46% of aneuploid). However, no difference was detected between the day of biopsy and ploidy. Interestingly, a significant difference (p=0.0071) was detected regarding blastocyst morphology: blastocyst with poor quality were more prevalent in the aneuploid group (16.95%) in comparison to embryos from euploid group (7.98%).

Conclusion

Poor quality blastocysts, classified as C in ICM and/or trophectoderm, have higher chances to be aneuploid. And for this reason, the possibility to biopsy these embryos should be very well evaluated. Our data also suggest that morphology assessment of day 3 embryos do not predict the ploidy status of the resulting blastocyst.

Keywords

ploidy, morphology, D3, blastocyst, biopsy day, PGT-A