Clinical application of human egg cryopreservation.

Clinical egg cryopreservation has been applied during a 4-year period with some limited success. Mostly mature and a few immature eggs were frozen slowly and thawed rapidly in 1,2-propanediol and sucrose, and subsequently inseminated by intracytoplasmic sperm injection (ICSI). Three studies were performed in which: (i) it was established that 55% of aged unfertilized mature eggs survive freezing; (ii) in 22 cycles of thawed donated eggs cryosurvival was 24% with 15 cycles reaching transfer, and five pregnancies were initiated, one of which went to term at 39 weeks with fraternal twin boys, and one remains ongoing at 37 weeks; and (iii) in five cycles, where in-vitro fertilization patients had some of their own eggs frozen/ thawed, cryosurvival of mature eggs was poor at only 2.2%, although 44% sibling germinal vesicle (GV) stage eggs survived. A normal female infant delivered at 40 weeks arose from transfer of two embryos where GV eggs underwent in-vitro maturation post-thaw and were fertilized by ICSI. Pregnancies reported here and by others indicate a burgeoning awareness of the potential benefits of egg cryopreservation, prompting cautious optimism for the future of this technology.