Blastocyst transfer is a method, by which fertilized eggs, already called embryos, are cultivated in the course of 120 hours in specific culture mediums for the purpose of optimum selection. The long-term in vitro cultivation allows “screening” of the embryos with best biological potential. On the other hand, long cultivation leads to stopping the growth of a high rate of genetically abnormal embryos.
Blastocyst transfer reduces the multiple pregnancy risk because of the small number of embryos transferred. Regretfully, this method cannot be applied in all cases, as a sufficient number of eggs must be aspirated and fertilized. The fact that the artificial cultivation medium is not the optimum condition for embryos growth must also not be forgotten.