Freeze-all, oocyte vitrification, or fresh embryo transfer? Lessons from an egg-sharing donation program

Area of Science:

• Reproductive Medicine
• Embryology
• In Vitro Fertilization

Background:

• Cryopreservation of oocytes and embryos is a key technique in assisted reproductive technology.
• Comparing outcomes of different embryo transfer (ET) strategies is crucial for optimizing fertility treatments.

Purpose of the Study:

• To compare the clinical outcomes of embryo transfers utilizing cryopreserved embryos, cryopreserved oocytes, or fresh embryos.
• To evaluate the impact of oocyte vitrification versus fresh oocyte insemination on embryo development and pregnancy rates.

Main Methods:

• An observational cohort study was conducted at a private university-affiliated fertility center.
• Included 8,210 mature oocytes from 425 donors; oocytes were used fresh or cryobanked.
• Compared outcomes of fresh embryo transfer, cryopreserved embryo transfer, and embryo transfer derived from vitrified oocytes.

Main Results:

• Embryos derived from vitrified oocytes exhibited decreased quality and lower blastocyst formation rates.
• The highest pregnancy and implantation rates were observed in the cryopreserved embryo transfer group (Thaw Cycles Group).
• Fresh embryo transfer cycles showed the lowest pregnancy and implantation rates.

Conclusions:

• Oocyte vitrification followed by intracytoplasmic sperm injection results in reduced embryo developmental competence compared to fresh insemination.
• Higher pregnancy and implantation rates can be achieved with embryo transfer into a more receptive endometrium, as seen in freeze-all protocols.
• The freeze-all method, involving cryopreservation of embryos, demonstrates exceptional clinical outcomes.