Embryonic blockage is the term used to refer to the fact that the embryos have not been able to form a blastocyst. They are normally embryos that usually stop developing on day +3/4 at the cell/morula stage.
Approximately between 50-60% of the embryos have the capacity to reach the blastocyst, the embryos that do not achieve this suffer the so-called embryonic arrest. Poor oocyte and seminal quality can be a reason for blocking the embryos. For example, it has been seen that sperm DNA fragmentation has a negative effect on embryonic development, producing a slower evolution of the embryos and being negatively related to embryonic arrest.
Another factor to take into account is the age of the oocyte. We know that the presence of chromosomal abnormalities in the oocyte increases with the age of the woman, influencing the embryonic genetic load and therefore its development. In addition, there are studies that show that one of the main causes of embryonic arrest is the presence of chromosomal abnormalities in the cells of the embryo. Specifically, it has been seen that almost 70% of the embryos that do not form the blastocyst have chromosomal abnormalities.
Advances and new technologies have allowed embryos to be cultured up to day +6 of embryonic development. The long culture allows us to select the embryos that have the capacity to form the blastocyst on day +5/+6 and, therefore, allows us a better embryonic selection. It will not be until day +3 of the culture when the embryo activates the embryonic genome, this activation is essential for the embryos to reach the blastocyst stage.