Reproductive aging, preimplantation genetic testing for aneuploidy, and the diameter of blastocysts: does size matter?

There is no doubt that maternal aging, also known as reproductive aging, can contribute to the increased rates of aneuploidy observed in blastocysts generated from women of advanced age who undergo <i>in vitro</i> fertilization (IVF). Additionally, the hatching process of the blastocyst, which is crucial for successful implantation, may be impaired in aneuploid embryos. Aneuploid embryos often exhibit abnormal cell division and chromosomal distribution, which can lead to disruptions in the hatching process. Due to ethical restrictions, preimplantation genetic testing for aneuploidy (PGT-A) is unavailable in all countries. Therefore, our retrospective study of 502 couples who underwent intracytoplasmic sperm injection (ICSI) aimed to elucidate if embryonic features, such as the ability to hatch and embryonic diameter, could be a reliable estimator for the success rate after embryo transfer, especially for women aged 26-45 years, and for IVF clinics which do not have access to PGT-A. The small hatching blastocysts (Bl. 5) group had a significant (<i>p</i> < 0.001) higher percentage of euploid embryos (≤35 Y- 73%, >35Y- 51%) compared to large (Bl. 4) counterparts (≤35 Y-58%, >35 Y- 38%). In patients aged 34-38 years, we detected 10% more euploid blastocysts in the hatching group than the expanding ones, which was a significant difference (<i>p</i> < 0.05). In conclusion, when selecting non-PGT-A tested embryos for embryo transfer (ET) or frozen embryo transfer (FET), a small hatching blastocyst seems to be a better choice than a large expanded one, especially for advanced-age patients for whom the risk of aneuploidy is higher.