How Long Can Frozen Eggs Be Stored?
Frozen eggs can be stored for more than 10 years. Currently, there is no definitive report on the maximum storage duration or a guarantee of 100% pregnancy success after thawing and use. The latest available data mostly covers eggs stored for about 4 to 5 years.
When thawed, the eggs are fertilized with sperm and the resulting embryos are implanted into the uterus, which can lead to a successful pregnancy. Medically, freezing eggs using liquid nitrogen is considered to effectively “pause” the aging process of the egg cells.
Therefore, it is widely believed that even after 10 years of freezing, the egg quality does not significantly deteriorate to the point where they cannot be used.
Why Can Frozen Eggs Be Stored for So Long?
The egg freezing process is not simply about retrieving eggs and freezing them immediately. It is a complex procedure designed to preserve the eggs’ quality as much as possible. Eggs are collected through the vaginal canal by specialized doctors in a sterile, temperature-controlled operating room to avoid any contamination.
Once retrieved, the eggs are immediately transferred to a laboratory where the environment is strictly controlled to maintain the optimal temperature for egg preservation. The eggs are carefully separated from other fluids with great delicacy, as they are very small—about the size of a needle tip—and extremely fragile.
After selection, the eggs undergo the freezing process. Freezing involves halting cellular activity by lowering the temperature to sub-zero levels while using protective agents to prevent cell damage. If freezing is done improperly or the eggs are exposed to excessive cold without protection, it can cause irreversible harm.
A critical part of egg freezing is storing them in liquid nitrogen at approximately –196 °C. There are two common freezing methods:
1. Slow Freezing: As the name suggests, the temperature of the eggs is gradually reduced at a rate of about 0.3 – 0.5 °C per minute, using computer-controlled equipment.
2. Vitrification: This is a more advanced method, used at Beyond IVF, where the temperature is rapidly lowered at a rate of 15,000 – 30,000 °C per minute. This technique minimizes the formation of ice crystals, which are the primary cause of egg damage during freezing.
Because of these precise steps and advanced technology, the eggs can be preserved safely for many years without significant deterioration.
What Happens to the Quality of Eggs After Freezing?
As everyone knows, freezing eggs essentially “pauses” their biological age, so the quality of the eggs remains the same without any deterioration. Naturally, eggs frozen at a younger and healthier age tend to have better quality compared to those frozen at an older age or when egg quality has already declined.
When the frozen eggs are thawed, there may be a slight decrease in quality, but it is usually minimal and not problematic. Additionally, children born from frozen eggs do not show higher rates of abnormalities compared to those conceived with fresh eggs. The quality of chromosomes is typically influenced more by the genetic makeup of the parents rather than the freezing process.
What Should Be Done When You Want to Use the Frozen Eggs?
- The frozen eggs are taken out and thawed.
- The eggs are then checked to confirm which ones are still alive and healthy, with a survival rate of about 90-95%.
- Fertilization is performed using the “ICSI” method (Intracytoplasmic Sperm Injection), where a single sperm is injected directly into each egg. This method is necessary because frozen eggs sometimes have a thicker and harder outer layer, making natural fertilization difficult.
- Once fertilized, the resulting embryos are placed back into the uterus to achieve pregnancy.