In human reproduction, the fertilized ovum is implanted into the endometrium when it has reached the stage of blastocyst that is at the 5^th or 6^th day after fertilization and not at the 2^nd or 3^rd day. The question was whether the transfer of day-2 or day-3 embryos is practically an obstacle to the synchronization between embryo and receptive endometrium which is essential for a successful implantation. Moreover, a theory was expressed that only embryos of good dynamics will manage to develop until the stage of blastocyst, having therefore more possibilities of being implanted. In vitro blastocyst culture has been made possible after the development of new appropriate culture media; however the results from the application of blastocyst culture and transfer did not fully meet the expectations. There is a common agreement among international IVF results published in medical literature that a routine adoption of blastocyst culture and transfer does not give better results than the traditional 2 or 3 day-old embryo transfer. Besides that, a large number of embryos do not manage to reach at the blastocyst stage in the laboratory without being sure that those embryos would not develop if they were transferred into the uterus at an earlier stage; this results in a reduced number of spare embryos for cryopreservation or even in IVF cycle cancellations due to lack of available embryos for transfer. Therefore, nowadays it is believed that the option of blastocyst culture and transfer should be discussed only for those couples with numerous (more than 3) failed implantations and provided that there is a large number of available embryos.