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OOCYTE BY JOHN A. SCHNORR, MD


There are two major innovations in the field of Reproductive Endocrinology which will revolutionize what we do and dramatically improve patient care. The first is the ability to successfully cryopreserve eggs with a high pregnancy rate. The second innovation would be the ability to mature immature eggs in test tubes so they can later be fertilized and transferred into a woman’s uterus with also a high pregnancy rate. Fortunately, there have been somemajor breakthroughs in the first innovation which is oocyte cryopreservation.


There aremultiple advantages to oocyte cryopreservation. One of themain advantages would be the ability to delay procreation which is especially applicable for patients with cancer who will undergo chemotherapy. Additional advantages include cryopreservation of eggs rather than embryos for ethical or religious reasons, to delay procreation for social reasons and the ability to salvage IVF treatment cycles which have gone awry frominadequate sperm specimens to ovulation disorders.


There aremultiple advantages to oocyte


cryopreservation. One of themain


advantageswould be the ability to


delay procreation which is especially applicable for patientswith


cancerwhowill undergo


chemotherapy.


Embryo cryopreservation first became successful in the mid 80s and remains amainstreamtechnique in


Reproductive Endocrinology care. There are, however, additional challenges that an egg poses rather than an embryo. The challenges posed by eggs include increased water content, amitotic spindle which is responsible for segregating chromosomes during the fertilization process, and the outer barrier to the egg, called the zona pellucida, which can harden with the freezing process. Early on in egg freezing technologies, we essentially use those same technologies that are successful with embryos and found lower egg survival rates along with lower fertilization rates and ultimately lower pregnancy rates. This technique is referred to as the “slow freeze” approach to oocyte cryopreservation.


The newer technique for oocyte cryopreservation is called vitrification and is a technique which requires the use of higher concentrations of cryoprotectant agents which first dehydrate an oocyte and then secondary agents are used which actually permeate the egg and stabilize the intracellular contents for the freezing process. The egg is then quickly cryopreserved in a fraction of a second by


literally plunging the dehydrated oocyte into liquid nitrogen. This process of aggressive dehydration and cryoprotection with the permeating agents and rapid


CRYOPRESERVATION: IS IT READY FOR PRIME TIME


THE RESOURCES LISTED IN THIS DIRECTORY ARE UNSCREENED AND SHOULD NOT BE VIEWED AS RECOMMENDATIONS OR ENDORSEMENTS, EITHER EXPRESS OR IMPLIED, BY THE AFA. 9


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