The principal goal of in vitro fertilization (IVF) is to obtain multiple eggs, fertilize them to form embryos, and then replace the most advanced one(s) into the uterus to achieve a viable pregnancy. Sometimes more embryos develop than can be safely transferred. When this occurs, suitable embryos can be cryopreserved (or frozen) for use in future cycles.

To prepare for freezing, the embryos are exposed to solutions that gradually remove water from the cells, since the main source of damage during freezing is the formation of ice inside the cells. Similar care must be taken when thawing embryos, as water must be added back to the cells.

Embryo Cryopreservation FAQ

What are the advantages of using frozen/thawed embryos?

There are several advantages:

1. the cost of the frozen cycle is dramatically reduced, as the embryos can be transferred with minimal or no medication;
2. frozen cycles are less complicated and do not require the same intensive monitoring and medication regimens found in a fresh cycle; and
3. if the timing isn’t right to transfer in the fresh cycle, the frozen embryos can be banked for future use.

How long can embryos be frozen for?

There is no data to support the maximum length of time that embryos can be frozen before they cannot be successfully used in IVF treatment. However, pregnancies have resulted from embryos frozen over ten years earlier.