The embryo is loaded into a small straw, and placed in the cooling chamber of a controlled rate freezer. The embryo is cooled slowly to maximize water extraction from the embryo and to prevent the formation of large ice crystals that can damage the embryo. The entire process takes several hours and the frozen embryo(s) are stored in liquid nitrogen at –1960 C.

Embryo thawing is simply a reversal of the freezing procedure. The embryos are removed from the storage tank and are warmed to room temperature in 30 seconds. For the next 30 minutes, the embryos are stepped through four different solutions until the cryoprotectant, the chemical used in the freezing solution to protect the eggs, is gone and all the water has been replaced. This thawing procedure is performed at room temperature. When completed the embryos are warmed to body temperature (370^oC). Thawed embryos  are ready for transfer to the mother 40 minutes after their removal from storage.

2. “How long can my embryos be stored?”

No one knows the maximum storage period. Procedures for human embryo freezing were developed in 1984 and went into widespread use in the late 1980’s. The longest time a human embryo was stored was 12 to 15 years. Patients who store embryos for this long usually do not return for them. Some patients have returned after 10 to 12 years and their embryos were thawed successfully. Beyond this time frame, it is not known for how long an embryo will remain viable.

3. “How am I going to be billed for storing my embryos?”

A precise inventory is maintained for all embryos in storage by the laboratory staff. The charge for embryo freezing includes the cost of storage for the remainder of the year. Patients with embryos in storage are billed six months in advance and are billed twice a year. It is the patient’s responsibility to notify RSC of address changes.

4. “What are my options if I/we no longer wish to store the embryos?”

Patients who no longer wish to store their frozen embryos have several options. Frozen embryos may be discarded as medical waste. They may be donated for research studies, in which case they are thawed, studied scientifically, and then discarded after a few days. Typical research topics include new techniques for freezing or thawing embryos, new ways of growing embryos in the laboratory, or understanding genetic composition of the embryos.

Patients have the option to donate their cryopreserved embryos to an embryonic stem cell research program at Stanford University. This program has been approved by Institutional Review Boards that ensure that the rights and welfare of human subjects are protected under Food and Drug Administration guidelines.

Lastly, patients may donate their embryos to other patients. RSC will help facilitate contact with agencies that specialize in matching frozen embryo donors and recipients. For patients who have an intended local recipient for their embryos, RSC will gladly coordinate the donation cycles.

5. “How are embryos discarded?”

To discard frozen embryos, a consent form must be signed by both partners, (as applicable), notarized, or witnessed by RSC staff. After a 60-day waiting period, at least two embryologists fulfill the patients’ wishes. They locate the embryos in the storage tank and carefully confirm the identity. The embryos are thawed and discarded. The embryologists initial and date the consent form and other storage documents, attesting that they performed and witnessed the disposition according to the patients’ wishes. The paperwork is kept in the laboratory files. If requested on the consent form, written confirmation of the disposal of the embryos is sent to patients.