The success of IVF with PGD, and therefore the probability of achieving a pregnancy, does not depend solely on the quality of the embryos. There are other factors that also influence the probability of achieving a positive IVF.
This is the case of the experience of the laboratory staff or the number of cells analyzed. When blastocysts are analyzed, the results of the analysis are more reliable. In addition, the ability of the embryos to compensate for cell loss must be taken into account.
Another aspect to be taken into account is whether the embryo transfer is fresh or deferred, i.e. using previously vitrified embryos.