user-circle-o search facebook linkedin2 twitter document-download info

Long Term Storage of Eggs and Embryos

Ultra-low temperature freezers are a standard fixture in laboratories and facilities needing to store chemicals, enzymes, and tissue samples, among other things, at steady, carefully regulated temperatures between about -45 to -86 Celsius. One of the most common and critical of these uses is cryopreservation, or, the long-term storage of living organisms, tissue samples, or cells, including frozen human eggs (oocytes) and embryos (fertilized eggs). 

What are Frozen Eggs & Embryos

Freezing human eggs and their fertilized future selves, embryos, are two ways fertility clinics have of preserving the opportunity for future use or donation. Women choose to freeze their eggs for a wide variety of personal reasons including:

  • Age & Personal Choice – Women may want to postpone pregnancy for a variety of reasons but opt to save their eggs while they are younger and eggs are at their healthiest.

  • Medical Treatments – Women undergoing radiation, chemotherapy, and other treatments or courses of medication may choose to save eggs before receiving medical treatments which may affect their eggs.

  • Medical Conditions & Diseases  – Women with diseases and conditions which may affect future fertility, such as autoimmune disorders, may opt to freeze eggs before the disease progresses to affect their fertility.

  • Fertility Treatments – Women undertaking fertility treatments, such as IVF, may choose to harvest multiple eggs at once, which can be used for multiple potential treatments in the future, rather than eggs being harvested for each individual round of IVF.

  • Transgender – Gender-affirming treatments can affect fertility, and some individuals choose to preserve eggs before undertaking such care.

  • Donation – Many women choose to donate eggs to others.

Success rates are similar between using freshly harvested and frozen eggs, making long-term storage an appealing option for women facing these choices.

How Are Eggs and Embryos Frozen?

Eggs and embryos are frozen, or, cryopreserved, using either a vitrification or a slow-freeze method. This cools them to low sub-zero temperatures (about -320 Fahrenheit), at which temperature they can be stored almost indefinitely.  Eggs can be frozen before or after fertilization for both short- or long-term shortage. The slow-freeze method requires the gradual addition of a cryoprotectant (like a cell-friendly antifreeze) over about 10 to 20 minutes which protects the egg or embryo during the freezing process. Then they are cooled in a machine that reduces the temperature a degree at a time until the necessary low temperature is reached. Vitrification is an extremely fast process in which eggs or embryos are combined with a stronger cryoprotectant than with slow-freeze techniques. To prevent the stronger cryoprotectant solution from damaging the eggs or embryos, they are immediately submerged into liquid nitrogen, converting them to a glass-like state, protecting them from damaging crystallization. With either freezing method, once the eggs or embryos reach the desired temperature (-196 Celsius or -320 Fahrenheit), the temperature of liquid nitrogen, they can be  safely moved to long-term storage.

How Are Frozen Eggs and Embryos Used?

When a decision is made to use frozen eggs or embryos, they are carefully removed from the freezer by teams who cross-check identification details to ensure accuracy. They are rapidly thawed to prevent ice formation during the temperature change, then multiple applications of water are used to replace the cryoprotectant material used to protect the frozen eggs and embryos.  Within about 40-45 minutes an egg or embryo retrieved from long-term storage can be ready for implantation. 

Long-Term Storage Solutions

For long-term storage, frozen eggs and embryos are transferred in liquid-nitrogen capsules to ultra-low temperature (ULT) freezers. While the record for storage time is about 30 years, most eggs are stored for under 10 years, and the majority are usually used within about 5 years. 

How Safe is Freezing Eggs?

Facilities storing frozen tissue understand the irreplaceable value of eggs and embryos and take the utmost care to ensure that every precaution is taken to ensure their safety and viability. Specialized systems monitor even the tiniest temperature changes, as minute as a hundredth of a degree, and on-site backup power is normally available as well. Over 90% of cryopreserved embryos and 85% to 90% of frozen eggs successfully survive the warming process. The length of time frozen seems to have little to no effect on the viability of frozen eggs and embryos with those that are five to ten years old routinely producing healthy babies.  

Types of Refrigeration Needed

Ultra-low temperature freezers are key to safely preserving frozen eggs and embryos. American Biotech Supply offers several sizes of USA-made, UL and C-UL listed ULT freezers for these deep sub-zero freezing needs.  Specific recommendations for long-term egg and embryo freezer storage include:

  • Appropriate Temperature Range – ULT freezers should consistently maintain the precise temperatures required for safe tissue preservation without damage or degradation.

  • Accurate Temperature Control – Microprocessor temperature controls allow for regulation to the finest level, assuring the protection of valuable contents.

  • Adjustable Temperature Change Alerts & Alarms – Programmable alarms with audible and visual alerts can monitor even the tiniest of temperature fluctuations.

  • Battery Backup – Power outages and fluctuations should not affect the safety of your eggs or embryos.

  • Security Features – Alerts, alarms, locks, and access controls maintain protection and security over freezer contents.

  • Insulation – Double-walled, insulated doors, additional urethane insulation for critical areas, triple-gasket seals, and vacuum relief ports ensure crucial temperature control and stability.

  • Environmentally-friendly Refrigerant – CFC-free, hydrocarbon refrigerants reduce energy consumption, offering increased efficiency over traditional, less environmentally-friendly refrigerants.

  • Adequate Size – Naturally, ULT freezers must offer enough room, preferably with standard-sized racks, to accommodate needed capacity.

  • UL/C-UL Listing Approval – As with all appliances, UL or C-UL listings ensure inspection and approval for standards of  electrical safety.

  • Cascade Refrigeration System – A cascade refrigeration system uses multiple evaporation-condensation cycles which overlap in sequence to reach desired temperatures smoothly.

  • Appropriate Voltage – ULT freezers are available to work with varying voltages, depending on your needs.

Ultra-low temperature freezers from American Biotech Supply meet these and more specifications, providing secure, superior deep sub-zero temperature security. You can trust our ULT freezers for safe storage of your most precious, irreplaceable contents. With sizes from 17 to 25 cubic feet and several voltages, our high-efficiency, low-noise ULT freezers are made in the USA and are ready to meet your egg and embryo cryopreservations needs. 


Please contact us to discuss the best possible solutions for your refrigeration requirements and needs

Contact Us via web


via email:

Customer Service