Find out more about cryopreservation of sperm, eggs and embryos to preserve your fertility and make your family planning more flexible.
Key Facts
- Cryopreservation is the freezing and long-term storage of biological material, such as sperm, eggs, embryos and even tissues, for later use.
- Two primary cryopreservation methods are used: slow freezing and vitrification (a rapid freezing technique).
- Embryos and eggs can generally be stored for up to 10 years
- Cryopreservation is usually an out-of-pocket expense for patients.
- Costs for cryopreservation may be covered by health insurance for certain medical reasons.
Introduction
Cryopreservation has revolutionised modern medicine, especially in the field of reproductive medicine and biotechnology. By preserving fertility, it allows couples and individuals to make more flexible choices about family planning and provides hope to those facing medical treatments that could compromise their ability to have children in the future.
What is cryopreservation?
Cryopreservation is a process in which biomaterials, such as sperm, eggs or embryos, are stored (cryopreserved) in liquid nitrogen at a temperature of -196 °C. This process involves cryobiology principles to ensure cell survival at very low temperatures. The material can then be used at a later date for fertility treatment, e.g., assisted reproductive techniques.
Types of cryopreservation
- Egg Freezing (Oocyte Cryopreservation): Women can choose to freeze their eggs to preserve their fertility. This can be beneficial for medical reasons, such as undergoing cancer treatment, or for personal reasons, such as career goals or delaying childbearing.
- Sperm Freezing (Sperm Cryopreservation): Men may opt to freeze their sperm for similar medical or personal reasons. In cases where sperm cannot be obtained through ejaculation, testicular tissue can be frozen and later used to retrieve sperm.
- Embryo Freezing (Embryo Cryopreservation): During in-vitro fertilisation (IVF), surplus embryos can be frozen for potential future use. This allows couples to attempt additional pregnancies without undergoing another full IVF cycle (frozen embryo transfer).
- Tissue Freezing and Transplantation (Testicular or Ovarian Tissue Cryopreservation): This technique offers hope to children and adolescents facing cancer treatments that may affect their future fertility. Testicular tissue or ovarian tissue is removed and frozen before treatment begins. After recovery, the tissue can be transplanted back, potentially restoring natural hormone production and, in some cases, fertility.
How does cryopreservation work?
1. Obtaining the Material
The first step is to carefully obtain the biological material intended for preservation. This process varies depending on what's being frozen:
- Oocytes (eggs): Eggs are collected through a process called egg retrieval, which involves hormonal stimulation to encourage egg development followed by a minimally invasive procedure to extract the eggs from the ovaries.
- Sperm: Sperm is typically collected through ejaculation. However, in certain cases where natural collection is not possible, sperm can be surgically retrieved from the testicles (TESE).
- Embryos: Embryos are created in a laboratory setting through in vitro fertilization (IVF) and may be cryopreserved if not immediately used for implantation.
- Ovarian Tissue: Ovarian tissue is obtained through a laparoscopic procedure, a minimally invasive surgery that uses a small camera and specialised instruments.
- Other Tissue: Depending on the specific type of tissue, it may be obtained through a biopsy or surgical removal. This includes tissues like bone marrow, which contains vital stem cells, or other mammalian cells used in research and tissue engineering.
2. Preparation and Treatment
The collected material undergoes meticulous preparation before freezing.
- Analysis & Cryoprotectant: The sample is carefully analysed for quality and then placed in a special solution containing cryoprotectants. These substances, such as dimethyl sulfoxide (DMSO) and glycerol, act like antifreeze, helping to prevent the formation of damaging ice crystals within cells during the freezing process. The permeability of the cell membrane to these cryoprotectants is a crucial factor.
Freezing Method: The type of material and its specific characteristics dictate the freezing method used, which is carefully outlined in established cryopreservation protocols.
- Slow Cooling: This traditional approach gradually cools the sample using a controlled rate freezer, allowing water to leave the cells and minimise intracellular ice formation. This method is often used for cell suspensions of various cell types, including red blood cells and hematopoietic stem cells.
- Vitrification: A newer technique, vitrification involves rapid cooling to transform the water within the cells into a glass-like state, avoiding the formation of ice crystals. It often offers improved cell viability, particularly for eggs and embryos. Vitrification solutions often contain high concentrations of CPAs to achieve this rapid freezing.
3. Freezing
The prepared material is placed in special containers (cryovials or straws) and then rapidly immersed in liquid nitrogen at a temperature of -196°C. This process is carefully controlled to minimise any potential harm to the living cells.
4. Storage
The frozen material is safely stored in specialised tanks filled with liquid nitrogen, maintaining the ultra-low temperature required for long-term preservation. Storage facilities adhere to strict safety protocols and regularly monitor temperature to ensure the integrity of the frozen samples.
5. Thawing (When Needed)
When the time comes to use the cryopreserved material, it undergoes a controlled thawing process. This gradual warming, with controlled warming rates, helps to prevent damage to the cells. The cryoprotective agents are then removed and the thawed material is carefully assessed to confirm its viability before being used in treatment. Factors like post-thaw viability and function are critical for successful cryopreservation.
When is cryopreservation used?
Cryopreservation of cells and tissue has become an invaluable tool in modern medicine and reproductive technology, offering solutions in various scenarios.
Key Applications of Cryopreservation
Fertility Preservation During Medical Treatment
Patients facing cancer treatments like chemotherapy or radiotherapy, or other medical procedures that may impact their fertility, can opt to cryopreserve their eggs, sperm, or even ovarian or testicular tissue before undergoing these treatments. This provides the opportunity to have biological children in the future, even if their fertility is compromised.
Social Freezing
Women and men who wish to postpone starting a family due to personal or professional reasons can choose to freeze their eggs or sperm. This proactive approach allows them to preserve their fertility at a younger age, when the quality of eggs and sperm is typically higher, increasing the chances of successful conception later in life.
In Vitro Fertilisation (IVF) Treatment
During IVF, it's common to create multiple embryos. Those not used in the initial cycle can be cryopreserved for future attempts, eliminating the need to repeat the entire IVF process each time. This is also beneficial for couples who may want to have children spaced further apart.
Gamete Donation
In countries where it's permitted, individuals can donate their sperm or eggs to be frozen and used by others who need assistance conceiving. This generous act helps individuals and couples struggling with infertility fulfill their dreams of parenthood.
Benefits of Cryopreservation
- The most significant benefit is preserving fertility for individuals facing medical conditions or those choosing to delay childbearing.
- In IVF, freezing embryos allows for single embryo transfer, reducing the chances of multiple pregnancies and associated risks.
- By cryopreserving embryos, couples have the opportunity to select the most viable embryos for transfer, potentially increasing the chances of a successful pregnancy.
Disadvantages of Cryopreservation
- Cryopreservation and associated procedures can be costly, and long-term storage fees add to the financial burden.
- While rare, there's a slight risk of cell or tissue damage during freezing and thawing. Additionally, there's no absolute guarantee that cryopreserved material will result in a successful pregnancy.
- The long-term storage of genetic material raises complex ethical questions, particularly around embryo ownership and the potential implications of future technologies.
How expensive is cryopreservation?
Cryopreservation itself typically ranges from CHF 400 to CHF 800 in Switzerland. However, it's important to understand that this is just one piece of the financial puzzle.
On top of the initial freezing cost, expect to pay an annual storage fee of roughly CHF 400. This can add up over time, particularly if you need to store the material for several years.
If cryopreservation is medically necessary, such as before cancer treatment, health insurance will usually cover the costs. It's always best to confirm this with your insurance provider beforehand.
For those choosing to freeze their eggs or sperm for social reasons, like delaying parenthood, the costs are generally not covered by insurance and must be paid out-of-pocket.
The initial price tag doesn't include the cost of any medications required, especially for egg freezing which often involves hormonal stimulation. These medications can vary significantly in cost depending on individual needs.
Some cryopreservation procedures, like egg freezing or sperm retrieval (TESE), may have additional associated costs for the procedure itself.
Remember that cryopreservation is just the first step. If you later choose to use the frozen material to conceive, you'll incur further costs for IVF or other fertility treatments.
Frequently Asked Questions
How long can sperm, eggs or embryos be frozen in Switzerland?
The storage period for spermatozoa, eggs and human embryos in Switzerland is regulated by law and varies depending on the type of biological material:
- Unfertilised eggs: 10 years
- Sperm cells: Indefinitely, as long as the donor is alive and able to provide ongoing consent.
- Embryos (fertilised eggs): 10 years
In some cases, extensions to the storage period may be granted. This can happen if there are medical reasons for the delay or if the couple can demonstrate that serious circumstances prevented them from using the stored gametes or embryos within the standard timeframe.
What is the pregnancy rate after cryopreservation?
The pregnancy rate after cryopreservation of eggs at reputable fertility clinics is generally comparable to, and sometimes even higher than the rate using fresh eggs. The survival rate of eggs after thawing is over 90%, and the pregnancy rates per embryo transfer range from approximately 32-65%.
Which fertility treatments are compatible with cryopreservation?
When using frozen unfertilised eggs, Intracytoplasmic Sperm Injection (ICSI) is the preferred method. This is because the egg's outer layer (zona pellucida) can harden during cryopreservation, making it more difficult for sperm to penetrate naturally. Traditional In Vitro Fertilisation (IVF), where sperm must fertilise the egg on its own, may therefore have a lower success rate in this scenario. In ICSI, a single sperm is injected directly into the egg, bypassing the hardened zona pellucida.
The success rates of ICSI using cryopreserved eggs are generally good and often comparable to those of ICSI with fresh eggs.
Takeaway
Cryopreservation, the process of freezing and storing biological material like sperm, eggs, or embryos at ultra-low temperatures (-196 °C), offers individuals and couples greater flexibility in their family planning. It is a particularly useful option for those facing medical treatments that could impact fertility, such as chemotherapy or radiation therapy.
