In Vitro Fertilization
Embryo Freezing
What is Embryo Freezing (cryopreservation)?
Embryo freezing involves storing viable embryos in sub-zero temperatures so that they can be used at a later date.
Why would a person freeze embryos?
After embryo transfer, some patients will have additional embryos remaining in culture. Couples frequently opt to freeze, or cyropreserve, these embryos for later use. In the event that a couple does not conceive with the initial “fresh” cycle, they may use cryopreserved embryos to attempt pregnancy at a much reduced cost; such “frozen” cycles also pose less health risks to the female.
Cryopreservation is also used in the event that a woman must delay pregnancy due to the risk of ovarian hyperstimulation syndrome, a condition that can place her health at risk.
Other women will opt for cryopreservation because they have been diagnosed with cancer. Some cancer treatments will destroy the eggs in a woman’s ovary and may leave her sterile. These women can go through IVF, freeze their embryos, receive their cancer treatment, and then when cured, use the embryos to attempt pregnancy.
What are the chances that frozen embryos will result in a successful pregnancy?
As with embryos obtained from a fresh cycle, the success of frozen embryos depends on the age of the woman at the time of retrieval, the stage and grade of the embryo, and the cause of infertility.
Embryos frozen at the blastocyst stage have the highest chance of resulting in a live birth. Cleavage stage embryos (pre-blastocyst) do not survive freezing as well as do blastocysts.
Can/Should all of my excess embryos be frozen?
This answer to this question is a matter of debate for doctors, patients and ethicists.
Some IVF centers will only freeze an embryo if it is a good quality blastocyst. The rationale behind this practice is that lower stage and grade embryos have such low success rates that freezing anything but the higher quality blastocysts gives the patients: 1) false hope, 2) additional expense without substantial chances of conceiving, 3) additional time lost for attempting another fresh cycle, which has a higher chance of pregnancy, 4) reduction of the number of embryos abandoned by couples who never return to collect them. Proponents of this view also say it is likely that the embryos frozen on day 3 that would most likely result in future pregnancy would have very likely made it to the blastocyst stage, whereas the embryos that would not have resulted in pregnancy would have stopped growing. Thus you are more likely to freeze only viable embryos and not bear the expense of freezing embryos destined to be non-viable.
The centers which have adopted this position have seen a dramatic rise in their success rates for frozen embryo transfers. There is wide variation in pregnancy rates after frozen cycles, with most centers reporting approximately 40-45% success rates after a frozen cycle using blastocyst embryos. This represents an improvement over the 10-20% chance of success with most day 3 frozen embryos.
Others would argue against this position on several levels: 1) false hope is relative, 2) even though the success rate of lower stage and grade embryos is lower, every embryo deserves a chance to succeed, 3) not all normal embryos will progress to the blastocyst stage, 4) due to cost or loss of ovarian function, some patients may never be able to perform another fresh cycle and cryopreserving more embryos gives patients more opportunities to achieve pregnancy.
As one can see, this is an issue with some complexity. Even in the same medical practice, different providers may have opposing points of view.
While we would prefer to freeze only high quality embryos on day 5, we must abide by our patient’s wishes and grant them the freedom to make an informed decision which best matches their ethical, moral, financial and emotional frame work and their physical health.
For these reasons, the decision on if to freeze, what to freeze and when to freeze must be given thoughtful consideration before the IVF cycle begins. Please bear in mind that no matter the outcome of the initial cycle, you will ultimately need to make the decision on how to use any excess embryos (see below). Having numerous unused embryos with no ultimate destination is a dilemma for both the couple and the clinic, as we would like to act responsibly with the embryos we help create and use them to create new life or further knowledge in the medical field when appropriate.
Besides freezing, what are the options for excess embryos?
- Disposal of embryos.
- Use of the embryos for scientific education or research.
- Donation of the embryos to another infertile couple.
What happens if we don’t want to use our frozen embryos?
You can opt for the same three choices mentioned in the previous answer.
What is the technique used to freeze embryos?
We use a process called vitrification, which has proven superior to the older “slow-freeze” technique.
What are the risks of cyropresevation?
There are no known malformations or developmental abnormalities associated with cryopreservation. The main risk is that the embryos simply won’t survive the freeze/thaw process.
What costs are involved in cryopreservation?
We initially charge for the first two years of storage. If you use the embryos within the first year, you will receive a portion of the charge back as a refund. After the first year, there is an annual charge. Please contact us if you have questions regarding the cost of cryopreservation.
How long can an embryo stay frozen and still result in pregnancy?
No one knows for sure. To date, 13 years is the record for the longest duration an embryo has been frozen and then resulted in a healthy, live baby. In general, we do not recommend freezing for more than 5 years.