Freezing, or cryopreservation, of embryos is a common procedure.
Since multiple eggs (oocytes) are often produced during ovarian stimulation, on occasion there are more embryos available than are considered appropriate for transfer to the uterus. These embryos, if viable, can be frozen for future use. This saves the expense and inconvenience of stimulation to obtain additional eggs in the future. Furthermore, the availability of cryopreservation permits patients to transfer fewer embryos during a fresh cycle, reducing the risk of high-order multiple gestations (triplets or greater). Couples who are concerned that their future fertility may compromised due to necessary medical treatment, such as cancer therapy or surgery, may also opt for cryopreservation.
Frozen embryos do not always survive the process of freezing and thawing. Freezing of eggs before fertilization is currently much less successful than freezing of fertilized eggs (embryos). Ethical and legal dilemmas can arise when couples separate or divorce; disposition agreements are essential. It is the responsibility of each couple with frozen embryos to remain in contact with the clinic on an annual basis. Pregnancy success rates for cryopreserved embryos transferred into the human uterus, called a frozen embryo transfer (FET), can vary from practice to practice. Overall pregnancy rates at the national level with frozen embryos are lower than with fresh embryos. This, at least in part, results from the routine selection of the best-looking embryos for fresh transfer, reserving the ‘second-best’ for freezing. There is some evidence that pregnancy rates are similar when there is no such selection.
Indications for Embryo Cryopreservation
- To reduce the risks of multiple gestation
- To preserve fertility potential in the face of certain necessary medical procedures
- To increase the chance of having one or more pregnancies from a single cycle of ovarian stimulation
- To minimize the medical risk and cost to the patient by decreasing the number of stimulated cycles and egg retrievals
- To temporarily delay pregnancy and decrease the risks of hyperstimulation (OHSS- see below) by freezing all embryos, when this risk is high.
Risks of Embryo Cryopreservation
There are several techniques for embryo cryopreservation, and research is ongoing. Traditional methods include “slow,” graduated freezing in a computerized setting, and “rapid” freezing methods, called “vitrification.” Current techniques deliver a high percentage of viable embryos thawed after cryopreservation, but there can be no certainty that embryos will thaw normally, nor be viable enough to divide and eventually implant in the uterus.
Cryopreservation techniques could theoretically be injurious to the embryo. Extensive animal data (through several generations), and limited human data, do not indicate any likelihood that children born of embryos that have been cryopreserved and thawed will experience greater risk of abnormalities than those born of fresh embryos. However, until very large numbers of children have been born following freezing and thawing of embryos, it is not possible to be certain that the rate of abnormalities is no different from the normal rate.
Important Decisions Regarding Cryopreservation
In Louisiana, all viable (living) embryos must be cryopreserved. No viable embryos are discarded. Prior to doing IVF, patients will sign a consent and statement outlining their choice with regard to disposition of embryos in a variety of situations that may arise (i.e. death of one parent, divorce, etc.) There are several options available to patients to help with their decision on cryopreservation of embryos.
We don’t want to freeze any embryos. This is a common concern of many patients due to ethical or religious convictions. In this case, we would simply fertilize only the maximum number of eggs that we would transfer (i.e. 2 or 3 eggs only). This choice may decrease the chance of pregnancy since the unfertilized eggs would be unused, but it would definitely eliminate difficult decisions later on.
We are okay with freezing our embryos, but what our our options later?
Transferring embryos in a primed / medicated cycle (best chance of pregnancy).
Transferring embryos in a natural cycle (least expensive option, but less chance of pregnancy).
Donating to another couple.
Transferring to a long term facility.
There are two methods for transferring cryopreserved embryos. First is a medicated/primed cycle. We prepare the patient ahead of time with medications to maximize the chance of success with the frozen embryo transfer (FET). Though this is a more expensive option, it is generally thought to be more successful. A second method is to transfer the frozen embryos in a natural cycle without medication or priming. The chance of success is still decent, but not as expensive or successful. Patients often choose this so they don’t have to choose other options such as donating to other couples.
We are concerned about our embryos getting mixed up with someone else’s embryos. Embryo security and proper identification is a top priority. In our lab, we only have ONE patient’s embryos out at a time. Each vial is labeled with a number and a name and cross referenced to their computer generated patient identification. The identification of the embryo is then confirmed by two embryologists and the physician. The identification of the patient is confirmed by the patient, her ID bracelet and the nurse. Prior to the actual embryo transfer, the patient’s name and number of embryos contained in the transfer catheter is called out for yet another confirmation. Any remaining embyros are cryopreserved and labeled with a number and a name. Storage records are contained in two separate locations. When transferring to a long term storage facility, a similar procedure is completed.
Where are our embryos stored (IVF patients – Lafayette Clinic)?
Your embryos are stored for one year at the ART Center at Women’s and Children’s Hospital. When they are initially frozen (usually the day after the fresh embryo transfer you will activate your account with a long term storage facility (we will arrange for this to be set up prior to the beginning of the IVF cycle). After one year, we will transfer them to this facility unless otherwise directed. If you choose to go through the embryo transfer within the year, no other storage fees apply. If after the first year they have not been used, you will be charged for the costs of transferring the embryos to the long term storage facility and for the costs of storage. When you are ready to use them, they can send them back to us immediately prior to the embryo transfer procedure.
Where are our embryos stored (IVF patients – Baton Rouge Clinic)? Your embryos are stored for one year at Fertility Answers’ Baton Rouge clinic. When they are initially frozen (usually the day after the fresh embryo transfer), you will activate your account with a long term storage facility (we will arrange for this to be set up prior to the beginning of the IVF cycle). After one year, we will transfer them to this facility unless otherwise directed. If you choose to go through the embryo transfer within the year, no other storage fees apply. If after the first year they have not been used, you will be charged for the costs of transferring the embryos to the long term storage facility and for the costs of storage. When you are ready to use them, they can send them back to us immediately prior to the embryo transfer procedure.