Which day should the embryo be transferred?

Over the past decade, improvements in culture conditions have allowed the possibility of extended embryo culture until day 5, which has been increasingly preferred to a transfer at day 2 ( cleavage stage) or day 3. In fact, day 5 blastocyst transfer is considered more physiological compared with transfers at day 2 or day 3.

It theoretically enables a better synchronization between the embryonic stage and the endometrial receptivity.

Moreover, it is well known that not all embryos obtained at day 2 develops to day.

Microscopic appearance at day 2 mostly isn't enough to predict their implantation potential .

To select embryos at day 2 or day 3 are insufficient to predict their developmental potential, notably because, in many cases, they fail to discard chromosomally abnormal embryos