Embryo Cryopreservation is an in Vitro Fertilization treatment process that involves the use of hormones to stimulate the development of multiple eggs. These eggs are than retrieved and fertilized in the laboratory. In many cases, more embryos are created than can reasonably be transferred to the woman’s uterus. If the excess non-transferred embryos are of good quality, it is the patient’s choice that they may be cryopreserved (frozen) so that they may be transferred at a future date. Embryo cryopreservation provides the opportunity to have an additional embryo transfer without the inconvenience and expense of a full IVF cycle.

The Center for Reproductive Health's IVF laboratory staff evaluates embryos under the microscope to assess quality. Various aspects of the embryo are evaluated based on standardized laboratory criteria. Cell shape, size and number are just a few of the features evaluated. The embryos selected for transfer are the highest in quality, or grade, to provide the optimal chance for pregnancy. Please note; the embryos are not being evaluated for genetic characteristics. Embryos may be frozen at any stage between day 1 (pronuclear stage) and day 6 (Blastocyst stage) after egg retrieval.

After placing the embryos in a cryoprotectant solution, they are frozen in a computer-controlled device designed specifically for embryo cryopreservation. Long-term embryo storage is in liquid nitrogen, at a temperature of -320°F (-196°C).

The cryopreserved embryos are thawed and replaced during a hormonally controlled cycle. It has been proven that 60 to 90% of the cryopreserved embryos successfully survive the freeze/thaw process. The stage and quality of the embryo at the time of freezing plays a major factor in the survival rate as well. The pregnancy rate after transfer of these embryos is similar to that of fresh embryos.

Prolonged periods of cryopreservation have been found to have no apparent affect on embryo viability. Embryos thawed after several years of cryostorage fare as well as those frozen for only one or two months. Since 1983, the cryopreservation procedure has resulted in the birth of thousands of babies worldwide. With this extensive experience, there have been no reports of any increase in birth defects as a result of cryopreservation.