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What actually IS egg freezing?

Updated: Oct 13, 2022

Egg freezing allows us to use our own eggs, frozen when they were young and healthy, to help us get pregnant later—if we might have otherwise had difficulty conceiving naturally.

Egg freezing, also called "oocyte cryopreservation", is a medical procedure to preserve fertility potential. It offers us the chance to preserve our eggs at their current age, so that we have the option for them to be thawed, fertilized, and transferred to our wombs in the future in the hope of leading to pregnancy. How does it work?In an egg freezing cycle, hormone injections are used to stimulate your ovaries to mature more eggs than usual that month. The resulting eggs are then retrieved in a short out-patient procedure by a fertility specialist. The eggs can be frozen and stored for an indefinite period of time. Why freeze your eggs?If you encounter problems getting pregnant naturally in the future and need to have IVF, thawing and using your younger eggs will increase your chances of having a healthy baby.

The growing uptake of egg freezing is based on the unfortunate truth that we are born with a finite supply of eggs at birth and both the quality and quantity of those eggs decrease as we age. That's because as we get older, a decreasing percentage of our eggs are considered genetically normal and able to lead to a healthy, live baby. When is the best time to freeze your eggs?

Biologically speaking, the best time to freeze your eggs is in your teens or twenties. However, in the real world, that might not represent good value for money. You don't know how life will pan out and the cost is not insignificant. However, if you leave it too late, your chances of both freezing good quality eggs and a good number of eggs declines. As such, an algorithm run by researchers at Harvard Medical School found 37 currently represents the "best" age to freeze your eggs in terms of value for money, when balancing all the factors. It's worth noting, though, that most doctors recommend freezing before 35 years old.

Does it work? The procedure is in no way a guarantee of pregnancy in the future. Though techniques are constantly improving, egg freezing still functions merely as an insurance policy. Vitrification, a relatively new flash-freezing technique, has almost universally replaced the old "slow freezing" technique and led to better odds. Vitrification is more effective because it reduces the chance of damage to the egg, leading to higher rates of egg survival after freezing and thawing and better overall egg freezing success rates.

Are frozen eggs worse than fresh?

Studies have shown that freezing and thawing eggs have no effect on the chance of pregnancy when using those eggs during in vitro fertilization. This was determined during a large randomized controlled trial published in 2010.

In 600 women undergoing in vitro fertilization treatment with eggs from an egg donor, half the cycles used “fresh” (recently retrieved, never frozen) eggs and half used eggs that had been frozen and thawed. The result: ongoing pregnancy rates were essentially the same between the two groups, and researchers concluded that frozen and thawed eggs were in no way inferior to fresh. That means that a woman who froze her eggs at age 30 years old and then thaws them to use at 40 years old has approximately the same chance of achieving pregnancy as she would have had using those eggs in an IVF cycle at 30 years old— effectively stopping the clock on her fertility. It also means that egg freezing success rates directly correspond to the age at which a woman froze those eggs. Despite age being the number one predictor of fertility, there are many other factors that come into play, such as medical history and lifestyle. Your own suitability for the procedure and chances of success are unique to you and can only be understood after a thorough assessment and consultation with your fertility doctor.


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