Egg freezing or oocyte vitrification is a rapid freezing technique for eggs and embryos, dramatically increasing their survival rate. It is a straightforward procedure and requires practically no programmable freezing equipment.
Human eggs have high water content and are therefore extremely fragile and sensitive to all freezing procedures. Conventional controlled rate slow-freezing methods do not always succeed because they allow some intra-cellular ice crystal formation that causes some damage to embryos, and severe damage to most eggs, rendering them unusable.
However, vitrification avoids the damage caused by crystal formation inside the cell, increasing their survival rate dramatically.
* Cryopreservation of sperm is also possible: sperm freezing
Cryopreservation for fertility preservation
EmBIO IVF Center is pleased to offer the service of cryopreservation (freezing) for women interested in preserving their fertility for the future. Egg or embryo freezing for fertility preservation can benefit a broad range of women - from cancer patients undergoing chemotherapy or radiation to women who anticipate starting or adding to their families later in life.
While a woman's uterus can carry a pregnancy to term well into her 40s, the decline in egg quality reduces the likelihood of a successful pregnancy. As a result, over 10,000 European women per year are forced to turn to egg donation in order to conceive. Egg freezing allows women to become their own donors earlier in life.
For women interested in exploring the option of egg freezing, please contact us for more information.
Egg freezing process
In the process of vitrification, an oocyte is placed in a minimal volume of a super high concentration of antifreeze medium (DMSO and ethylene glycol) for a brief period of time and cooled at an extremely rapid rate. The fast freezing eliminates the formation of ice crystals in the oocyte (egg). The water inside the cell just instantaneously super cools into a solid with no ice crystal formation. With conventional “slow freezing,” the temperature of the egg and embryo goes down at precisely 0.3°C per minute.
With vitrification (using four times the concentration of antifreeze or cryoprotectant), the temperature is dropped to 20,000 degrees °C per minute, which is 70,000 times faster. At that speed of cooling and at that concentration of antifreeze, ice crystals simply cannot form. The egg survival rate is approximately 90%. After the vitrification, the oocytes/embryos are stored in liquid nitrogen until such time as it is to be thawed and fertilized or transferred.
Following IVF treatment, more embryos may be created than can reasonably be transferred to the woman’s uterus. In approximately 25% of IVF cycles, the remaining embryos are of sufficient quality to be frozen and stored for future use, allowing couples to have an additional embryo transfer without the expense of a full IVF cycle.
In all cases, the embryo freezing procedure involves placing the embryos in a cryoprotectant solution and cooling them under controlled conditions. Then the embryos are stored in liquid nitrogen at a low temperature (-196°C). Considerable care is taken to minimize the possibility of damage caused by the whole procedure.
Embryos can be frozen at any stage between day 1 (2PN stage) and day 6 (blastocyst stage) after egg retrieval. Only high-quality embryos are cryopreserved because they are far more likely than others to survive and be capable of further development after freezing. Depending on the embryo stage at the time of freezing, between 60-90% survive the freeze/thaw process resulting in a future pregnancy. Cryopreserved embryos are placed in the uterus during either a natural menstrual cycle or a hormonally controlled cycle.
Risks and limitations of egg or embryo freezing
However, this method is not quite as simple as it might seem. The high concentrations of cryoprotectant, even for a few minutes, could be toxic to cells. Therefore, the eggs and embryos must first be placed in lower concentrations of antifreeze and sucrose to draw some water out of the cell and then left in high concentrations for less than a minute before instantaneous freezing. During thawing, the embryos and eggs must be instantaneously warmed, immediately taken out of the high concentration of antifreeze, and then placed into a solution with a lower concentration to avoid antifreeze toxicity. The whole process requires more skill than conventional freezing, but it is faster, cheaper, and, most importantly, avoids almost all freezing damage to either eggs or embryos.
Who can benefit from oocyte or embryo vitrification?
Such a reliable method of egg and embryo freezing gives the IVF program a much greater ability to avoid a dangerous pregnancy with more than one fetus. It also makes scheduling for many procedures like egg donation simpler for the patient (oocyte banking). In addition, this dramatic new technique offers hope to women of reproductive age, especially:
- Young women who want to preserve their fertility for the future if they wish to delay childbearing but not lose their fertility as they age. With vitrification, eggs and embryos are reliably preserved, so the pregnancy rate is no different than if the embryos or eggs had never been frozen.
- Women who want to freeze their eggs because they haven’t found a partner yet. As a woman ages, her fertility declines, and the rate of spontaneous abortion rises. Moreover, the risks of chromosomal abnormalities are higher in older women.
- Women who are diagnosed with cancer and want to preserve their healthy oocytes before starting radio/chemotherapy. In this way, they preserve their ability to start a family in the future.
- Women who want to freeze their embryos after an IVF cycle for future use.
- Women with premature ovarian failure.
Fertility preservation for cancer patients
Being diagnosed with cancer is tough enough to deal with. But if you want to have a child, you may feel an added level of anxiety. Family-building options are available after cancer treatment. The earlier you understand those options, the greater your chances of preserving your fertility.
Treatment is available for couples who have been diagnosed with cancer. It is important that you raise this issue with your treating doctor early in the process. It is best to see a fertility specialist early in your evaluation. However, post-treatment options are also available.
- Radiation and chemotherapy can damage eggs.
- If appropriate, eggs can be removed from the ovaries before treatment, and in vitro fertilization can be performed. The resulting embryos can be frozen for use after treatment.
- If eggs have been damaged during cancer treatment, egg donation is an excellent option for many women.
- sperm can be frozen before treatment begins (sperm cryopreservation).
- in vitro fertilization with an advanced technique to help sperm get into the egg (ICSI - IMSI) is a possible option after sperm freezing.
- if sperm production has been affected by treatment, sperm donation is another option.
At EmBIO IVF Center, we understand the emotional impact of being diagnosed with cancer and the added concerns about building a family. We are here to help you understand your options and will see patients diagnosed with cancer on very short notice.
Our expert fertility team will be glad to guide you in your fertility treatment.