January 20, 2024

Frozen Embryos: The Science and Choice Behind Long-Term Storage


Embryo cryopreservation is a significant advance in assisted reproductive technology, providing hope for individuals and couples facing challenges in becoming parents. This method allows for the safe storage of early-stage embryos. It offers an opportunity for people to pause and thoughtfully make crucial decisions about their family's future. Additionally, this technique opens up the possibility of donating embryos to others in need. This approach not only supports those directly involved but also underscores the value of life and celebrates family.


embryo lab frozen preserved

Understanding Embryo Cryopreservation


Embryo cryopreservation involves the freezing and storage of fertilized eggs (embryos) at ultra-low temperatures, typically around -196°C (-321°F), using advanced techniques such as vitrification or slow freezing. This process halts all biological activity within the embryos, preserving their viability for an extended period. The primary goal is to provide individuals with the option to use these embryos at a later date, offering hope for future pregnancies. This innovative process has several key aspects:

  • Halting Biological Activity: At these ultra-low temperatures, all biological activity within the embryos is stopped. This suspension is crucial for preserving the embryos without aging or degrading.
  • Preservation of Viability: This process is designed to maintain the viability of the embryos. When properly stored, these embryos can remain frozen for many years, retaining their potential for successful implantation and development.
  • Future Use for Pregnancy: The primary goal of embryo cryopreservation is to provide individuals or couples with the option to use these embryos at a later date. This is particularly beneficial for those who might face fertility challenges or for those who wish to add multiple children to their family.


Reasons Someone Might Choose Frozen Embryo Storage


Fertility Treatment:

After undergoing fertility treatments like in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI), individuals often end up with surplus embryos. Freezing these embryos allows them to be stored for later use, providing a potential solution for subsequent attempts at pregnancy. This is where the term snowflake children comes from.

Preserving Fertility in Medical Interventions:

For individuals facing medical interventions that may impact fertility, such as cancer treatments or hormone therapies, embryo cryopreservation becomes an option. It offers the opportunity to safeguard fertility before undergoing treatments that might compromise reproductive capabilities.

Delaying Parenthood:

Some individuals and couples choose to delay parenthood. Freezing embryos provides a way to preserve fertility at a younger age, allowing for family planning at a more suitable time.

Preimplantation Genetic Testing:

During fertility treatments, when preimplantation genetic testing (PGT) is utilized, there's an option to freeze embryos following the testing. This method is available by medical professionals, but not allowed by Nightlight for adopted embryos.



Embryo Storage lab


The Cryopreservation Process







First - Dehydration:

Embryos slated for cryopreservation undergo a dehydration process. They are exposed to a cryoprotectant solution, replacing the water inside the embryos. This step protects the embryos from ice crystal formation during freezing.

Second - Vitrification:

The embryos, now dehydrated, undergo vitrification. They are carefully placed in containers and rapidly immersed in liquid nitrogen. This results in the formation of a glass-like solid, preventing ice crystal formation and minimizing potential damage to the embryos.

Third - Storage:

Vitrified embryos are transferred to long-term storage tanks filled with liquid nitrogen. These tanks are designed to maintain extremely low temperatures, ensuring the embryos' preservation for extended periods, often exceeding 10 years.


Challenges and Considerations

  • Potential Damage During Freezing:

While the cryopreservation process is highly advanced, there is the potential for damage to embryos during freezing. Thawing procedures are equally critical, and the viability of embryos post-thaw must be carefully assessed.

  • Ethical Dilemmas:

The prolonged storage of frozen embryos pose ethical dilemmas, especially when individuals or couples decide not to use them. Decisions regarding donation to others are critical for the life of a snowflake baby. It's important to weigh all the those affected when making such a decision.


The Science of Thawing and Implantation


When individuals or couples decide to use their frozen embryos, the thawing process initiates. This involves carefully retrieving the desired number of embryos from storage. The process involves rapidly warming the embryos. This step is critical; it must be done quickly and accurately to ensure the embryos are not damaged while reactivating their biological processes. After they are warmed, the embryos undergo a thorough assessment to determine their viability. It's essential to confirm that the embryos have survived the freezing and thawing process without any detrimental effects and are capable of continuing normal development.


Success Rates and Outlook


The success of frozen embryo transfer varies based on several factors, including the overall health of both partners, the age of the woman during egg retrieval, the presence of fertility issues, and the history of previous fertility treatments. Research continues to explore whether fresh or frozen embryos offer better chances of successful pregnancies.


Unused Frozen Embryos: Choices and Considerations


For those with frozen embryos that remain unused, one can prayerfully consider the options. There is the altruistic choice of donating these precious gifts to others who are on their own journey to conceive, an act of profound generosity and compassion. In making these decisions, it's essential to engage in a prayerful and thoughtful reflection, considering personal beliefs and ethical implications, always seeking guidance and wisdom in this significant choice.


Embryo cryopreservation, with its scientific advancements and evolving choices, has transformed the landscape of reproductive medicine. The ability to freeze embryos provides individuals and couples with opportunities for family building that were not previously possible.

Learn more about our process and how you can donate your frozen embryos through our Snowflakes Embryo Adoption program.

By Beth Button

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