USC Fertility

Embryo Freezing

Embryo freezing offers more flexibility in pregnancy planning

In addition to the recent advancement of improved egg freezing, embryo freezing is yet another option that can be combined with the IVF process. Embryo freezing enables couples to keep multiple embryos for more than one attempt at pregnancy.

When a prospective mother goes through an IVF treatment, multiple healthy embryos may be produced. Prior to freezing, your USC fertility specialist will work with our embryologists to determine which embryos would most likely produce the best possible pregnancy.

Slow freezing and vitrification

Embryo freezing was originally performed in a slow-freeze method, and the probability of success was limited due to ice crystals forming within the cells. A more advanced, ultra-rapid freezing method called vitrification was developed to significantly increase the probability that an embryo would remain competent through the entire freezing and thawing process.

Vitrification is now considered standard protocol. With embryo freezing, we replace the water content with a cryoprotectant before fast-freezing and long-term storage in liquid nitrogen.

When to opt for embryo freezing

In some cases, prospective parents may need to delay their pregnancy, such as when the woman requires chemotherapy treatment or has committed to pursuing educational or career goals.

In other situations, embryo freezing may be performed so that the IVF patient does not have to incur the expense of the entire IVF process again on a subsequent attempt. Also, gay or lesbian couples who want more than one child can freeze their embryos in order to bypass the IVF procedure for their subsequent pregnancies.

Assessing the embryo’s competence

Fertility specialists and embryologists conduct a visual assessment around the third day after fertilization, noting the shape of the embryo and its cells, cell numbers and growth rates. Of course, other factors also play key roles in the quality of the embryo, including chromosomal integrity—the most important characteristic of having exactly 46 chromosomes. Otherwise, chromosomal deficiencies may affect the baby with conditions such as Down’s syndrome, especially when the mother is over the age of 35.

Preimplantation genetic screening enables us to examine an embryo’s DNA prior to freezing, so ask your fertility specialist about this informative test.

Options for frozen embryos

When a couple decides that their family is complete, the issue of what to do with leftover frozen embryos must be addressed. Following are some options available to couples with surplus frozen embryos.

Storage: Until a couple is sure that their family building is complete, they may opt to keep frozen embryos, but would need to continue paying storage fees.
Compassionate transfer: The embryos are transferred back into the mother’s uterus when she is least likely to get pregnant.
Discarding: When a couple is certain that they no longer want to have children, the leftover embryos may be thawed and discarded. Legal documents will need to be signed for this release.
Research donation: If your frozen embryos meet certain criteria, the medical community may be able to accept and make great use of them in advancing embryo cryopreservation.
Donation to others: Other prospective parents may be thrilled to receive your embryo donations, in the case that legalities allow for it.

Contact USC Fertility to learn more about whether embryo freezing options may be appropriate for your fertility expectations.