The fancy scientific name for egg freezing is “oocyte” (egg) “cryopreservation” (freezing). Cryopreservation is a decades-old procedure used in several branches of medicine. The basic premise is this: cooling cells, in this case egg cells, to a very low temperature (think -196º Celsius, or about -320º Fahrenheit) stops all cell activity, including aging. In layman’s terms, that means that freezing your eggs prevents them from aging as they normally would, maintaining their youthful glow (and lack of chromosomal defects) indefinitely.
There are two different methods used to get eggs to this low temperature: vitrification, a flash freezing technique, and slow freezing, which is, well, exactly what it sounds like. There’s tons of evidence that vitrification is the more effective technique 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. Here at Extend Fertility, we use Cryotec vitrification, the most advanced method of cryopreservation available, resulting in a near 100% egg survival rate. Though a 100% survival rate doesn’t necessarily mean 100% of the eggs will be fertilized and lead to pregnancy, it’s the best possible place to start when or if you use your frozen eggs. Learn more about egg cryopreservation at Extend Fertility.
Egg freezing helps women get pregnant later for two primary reasons.
Firstly, young eggs are more likely to be genetically normal. That’s because women are born with all the eggs they’ll ever have, and as they age, the DNA inside their eggs is inevitably affected by damaging, but mostly unavoidable, influences like fevers, infections, stress, toxins, and free radicals. Since DNA is like an instruction manual for cells, any damage to it can prevent that cell from doing what it’s supposed to do—which, in the case of the egg, is make a healthy baby.
So as women get older, they’re left with a lower percentage of their overall egg count that’s genetically normal. (This issue is known as egg quality.) But if a woman’s eggs are frozen while she’s still young, those eggs will avoid the damage that comes with age, and be more likely to lead to a healthy pregnancy.
Secondly, egg freezing works because the process of freezing and thawing eggs has no effect on the chance of pregnancy when using those eggs during in vitro fertilization. This was determined during a large randomized controlled trial (the most reliable kind of study researchers can do) published in 2010. From a population of 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 and thawed them for use at 40 has approximately the same chance of achieving pregnancy as she would have using those eggs in an in vitro fertilization cycle at the time she froze—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. Learn more about egg freezing success rates.