Yes, indeed the implantation rate can be improved, and to achieve this it is sufficient to adjust the moment of implantation to the affinities of the endometrium and the moment of maturation of the blastocyst.
In order to be fertilized, the egg must present a specific character at a given moment. On the other hand, the same thing happens to the endometrium, but with the difference that we have the ovum under the microscope to study it, and in the case of the endometrium we cannot do the same. We use indirect methods -progesterone and endometrial imaging- to find out if it is receptive, in order to transfer the embryo when its conditions allow it. And sometimes that moment is not the right moment for the endometrium. If we are in this situation, we should get the embryos and cryopreserve them until the right time to transfer arrives. We must prepare the endometrium and when it presents the ideal conditions, transfer the cryopreserved embryo that we have available. In this case, we are dealing with a delayed transfer.
Another option we have is to prepare the endometrium for the cryotransfer and once the time is right, take an endometrial biopsy (ERA test, Endometrial Receptivity Test) and not transfer the embryo. This process forces us to repeat the endometrial cycle to transfer the embryo. It is a process that is more time-consuming and costly, but at the same time it gives us the certainty of knowing if we are at the perfect moment to perform the embryo transfer and thus achieve better results.