OBJECTIVE: To compare the outcomes of ETs using cryopreserved embryos, cryopreserved oocytes, or fresh embryos.DESIGN: Observational, cohort study.SETTING: Private university-affiliated fertility center.PATIENT(S): This study included 8,210 mature oocytes obtained from 425 oocyte donors. Of those, 5,440 were used for the donors' own cycles (Fresh Oocyte Cycles Group), and 2,770 were cryobanked for 425 recipients (Banked Donor Egg Group). All of the oocytes were sperm injected, resulting in 4,585 embryos from the donors' own cycles and 2,128 embryos from the recipients' cycles. For the donor cycles, embryos were either cryopreserved and transferred during a subsequent cycle (Thaw Cycles Group, 3,209 embryos), or they were transferred during a fresh cycle (Fresh Cycles Group, 1,307 embryos). For the recipient cycles, embryos derived from vitrified oocytes were transferred (Vitrified Oocytes Group, n = 425 cycles, 2,128 embryos).INTERVENTION(S): Oocyte/embryo vitrification and intracytoplasmic sperm injection.MAIN OUTCOME MEASURE(S): Embryo quality, pregnancy, and implantation rates.RESULT(S): Decreased embryo quality and lower rates of blastocyst formation were observed among embryos derived from vitrified oocytes. The highest pregnancy and implantation rates were noted for the Thaw Cycles Group, followed by the Banked Donor Egg Group; the Fresh Cycles Group had the lowest rates.CONCLUSION(S): Oocyte vitrification followed by intracytoplasmic sperm injection leads to lower embryo developmental competence compared with when fresh insemination methods are used. However, pregnancy and implantation rates are higher when embryos are transferred into a "more receptive" endometrium, free of the adverse effects of gonadotropin. Moreover, the freeze-all method leads to exceptional clinical outcomes.
Adult Blastocyst