Vitrification can significantly increase the chances of pregnancy after IVF and preserve viable embryos remaining after an IVF cycle. This is one of the most important advantages of cryopreservation.
Freezing all embryos for future transfer into the uterine cavity may be recommended for women at increased risk of developing severe ovarian hyperstimulation syndrome (OHSS) following ovarian stimulation during an IVF cycle, as well as for patients who are preparing to undergo radiotherapy or chemotherapy for cancer treatment. Embryo vitrification may also be indicated whenever the likelihood of implantation is reduced, for example, in the presence of an endometrial polyp, insufficient endometrial thickness at the time of transfer, or dysfunctional uterine bleeding. It may also be recommended when embryo transfer during an IVF cycle is difficult because the catheter cannot be passed through a narrowed cervical canal into the uterine cavity (cervical stenosis).
Freezing may also be incorporated into an egg donation cycle when, for any reason, it is difficult to synchronize the menstrual cycles of the donor and recipient. A cryopreserved (thawed) embryo can subsequently be transferred into the patient’s uterine cavity without the need for another cycle of ovarian stimulation and egg retrieval.
The chance of pregnancy after the transfer of thawed embryos may be higher than with fresh embryo transfer. Therefore, we strongly recommend cryopreservation by rapid freezing (vitrification), particularly for patients who have additional viable embryos remaining after an IVF cycle. Approximately 50% of patients undergoing IVF may have additional embryos suitable for cryopreservation. A frozen embryo transfer cycle is significantly less expensive than undergoing a new IVF cycle, and having cryopreserved embryos provides patients with an additional opportunity to achieve pregnancy if the initial transfer is unsuccessful.