Embryo Cryopreservation

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The cryopreservation (freezing) of embryos is utilized when the number of embryos produced during any IVF cycle exceeds the number of embryos that are transferred into the uterus. Embryos can be subsequently thawed and placed into the uterine cavity after many years of being frozen. By doing so, one can avoid repeating the entire stimulation and egg retrieval process for future attempts.

At Advanced Fertility Care, we are very selective as to the quality and grade of embryos we freeze. While some fertility centers may freeze a high percentage of embryos, one must remember that quantity alone is not sufficient; it is the overall quality of the embryo that will lead to a successful freeze and thaw, and ultimately a pregnancy resulting from a frozen embryo transfer. Only better quality embryos will be able to endure the stress of the freeze and thaw process. Freezing a large number of poor quality embryos only serves to provide a false sense of security and hope to a couple that their future reproductive potential is still present given the number of embryos they have frozen. Despite our selectivity, approximately 40-50% of patients undergoing IVF at Advanced Fertility Care will have at least one high quality embryo to freeze after a fresh IVF cycle.

Prior to the last few years, traditional embryo cryopreservation occurred using a slow freezing process. However, over the last several years the process of vitrification (rapid freezing of embryos) has become extremely successful yielding higher pregnancy rates than traditional slow freeze methods of embryo cryopreservation. Only specially trained and highly skilled embryologists and appropriately equipped laboratories can perform this technique. As of early 2009, the embryologists at Advanced Fertility Care switched entirely to a vitrification system for embryo cryopreservation.

What is vitrification for IVF?

The actual scientific definition of vitrification is the process of converting something into a glass-like solid that is free of any crystal formation. Translated into embryology, vitrification is the use of an ultra-rapid embryo freezing process versus the traditional slow freezing process.

The most difficult part of freezing any cellular tissue such as embryos or eggs is that the water content within the cells from ice crystals during the freezing process which are very detrimental to the health of the cells. With the vitrification process, the addition of a cryoprotectant (similar to antifreeze in car’s radiator), allows water to be cooled until it hardens like glass without any ice crystals forming. This is important in the embryology world because ice crystal formation can be very damaging to frozen embryos (or other frozen cells). Therefore, vitrification in IVF can allow freezing of spare embryos (and eggs) with better post-thaw survival rates and higher pregnancy and live birth rates from frozen embryo transfer cycles.

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