Clinical application of human egg cryopreservation

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