Blastocyst is called an embryo at an advanced stage of development, after 5-6 days of culture. At this stage, the embryo is composed of 60-100 cells, which have begun to differentiate into two distinct groups, the outer and inner cell mass, and are characterized by the presence of the blastocoel.
Embryo transfer is done the same way, regardless of whether we are transferring embryos on day 2, 3, 5 or 6.
Embryo transfer at the blastocyst stage (and not earlier) is made depending on the background of each couple, the number and quality of the embryos. It is not advisable to carry embryos at the blastocyst stage as a routine practice for each case, because not all embryos reach this stage (it is estimated that only 40% of normally fertilized eggs become blastocysts). So, the decision of whether or not to have a blastocyst embryo transfer is up to the individual and each pair.