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Cryopreservation is the preservation and storage of embryos/oocytes at a very low temperature until they can be revived and restored to the same living state as before they were stored. These low temperatures are possible using liquid nitrogen which maintains the stored embryos and eggs at -196 degrees Celsius (-320.8o F). Human and mammalian tissues can be cryopreserved for prolonged periods of time and function normally after thaw.

For many years the process of cryopreservation has been successfully used in the reproduction of various animal species. Being able to cryopreserve excess/extra good quality embryos, allows us to transfer fewer embryos on the fresh cycle and still give the patient a second chance for a pregnancy on a subsequent cycle. A frozen cycle is much easier than a fresh cycle. It is our policy at The Center For Reproductive Medicine to follow the guidelines set by the American Society for Reproductive Medicine (ASRM) for numbers of embryos to transfer. With some exceptions the guidelines recommend the transfer of two good quality embryos in patients under 37 years old; 3 in patients 38-39; and, 4 or more in patients over 40 years old. The recommendations are in place to help control or limit high order multiple births without compromising pregnancy rates.

The Center's Embryology Team cryopreserves embryos by a procedure called vitrification. Prior to 2010 embryos were frozen, at The Center for Reproductive Medicine, by a slow freeze method. Vitrification involves rapidly lowering the temperature of the embryos approximately 600 times faster than the conventional slow freeze method. The rapid drop in temperature enables the liquid containing the embryo to transition directly to a solid (glass-like) state thus preventing any ice crystal formation. With the slow freeze method crystallization commonly resulted in damage to the embryo causing trauma or cell death. Since we began using vitrification we have above a 90% survival of our thawed embryos as compared to around 50% survival with the slow freeze method. Although only 12 patients so far at The Center have thawed their vitrified embryos the pregnancy rate with that group of patients is comparable to that of our fresh cycles.

In 2010 we began an IRB (Internal Review Board) approved egg (oocyte) freeze research program which has produced excellent results. Our main objective with this program was to provide female cancer patients an alternative to have a baby after losing their fertility as a result of chemotherapy. We currently have a survival rate of our thawed eggs of greater than 92% with a fertilization rate of 75% and a development to blastocyst equivalent to the use of fresh oocytes. We have transferred embryos into 4 patients with 3 pregnancies that we can absolutely say were from frozen eggs. What is even more remarkable is that one of these patients is pregnant from an FET(frozen embryo transfer) using vitrified/thawed blasts resulting from vitrified/thawed eggs. This is how far the field of cryopreservation has come. A "Double" freeze would have had little chance of success even 5 years ago. Now it will be common place.