Prolonged culture (embryo culture until day 5 of embryo development
Embryo culture in laboratory conditions up to the stage of expanded blastocyst, 5-6 days after fertilization. The success of blastocyst transfer is higher compared to transfers of embryos in lower developmental stages, because in a large number of embryos, the division stops between the day 3 and 4 of their development. The transfer of blastocysts prevents the transfer of those embryos which would stop developing during this period under laboratory conditions. The suitability of prolonged embryo culture is assessed by the number of fertilized oocytes and a number of other factors and should be discussed with the embryologist.