At many fertility clinics, the success rates of IVF with donor eggs are similar for both fresh or frozen donor eggs. As you might expect, fresh donor eggs are retrieved from the donor and fertilized immediately with sperm from the intended father or sperm donor. Fertilized eggs are incubated in the IVF laboratory for 5 days until they reach the blastocyst embryo stage, at which point they will be frozen for later transfer to the intended mother’s uterus or that of a surrogate. If preimplantation genetic testing (PGT) is planned, blastocysts are biopsied before being frozen.
If using frozen eggs, the intended mother or surrogate begins to prepare her uterine lining with hormones, so that 6 days before embryo transfer the frozen donor eggs can be thawed, fertilized, and allowed to develop to the blastocyst embryo stage in order to be synchronized with the uterine lining at the time of embryo transfer. Additional blastocysts are frozen for future use. If PGT is planned, frozen eggs are thawed, the resulting blastocysts biopsied, and then refrozen awaiting PGT results. In this setting, the intended mother or surrogate will prepare her uterine lining later when the PGT results return.
For frozen blastocysts derived from fresh eggs or blastocysts derived from frozen eggs, there is no need to synchronize the intended mother’s cycle with the egg donor retrieval cycle, thus providing convenience and alleviating stress.