“Social” egg freezing, the medical terminology for women who would like to preserve their fertility not because of an impending medical necessity – such as chemotherapy – but for reasons related to life choices, are interested in the choices that they have for preserving their fertility.
As a screening test, clinics will often use age to suggest whether or not freezing eggs is appropriate. By age they really mean egg quality, as we know that on average women will not have egg quality sufficient for ongoing pregnancy beyond the age of forty-one. Of course, this is just a statistical average; we all know women who will be able to achieve pregnancy into their mid-forties, but unfortunately, there will also be women who would struggle well before that.
Unfortunately, there’s no test that directly measures egg quality, so instead we test for egg quantity.
On average, it would take four to five fertilized eggs to create a blastocyst. A blastocyst is an embryo that ought to implant, though it may or may not be genetically viable, aka euploid (this is why many women become pregnant only to lose it in the first trimester: it was not a euploid blastocyst that implanted).
For women under thirty-five, on average about 70% of blastocysts will be euploid. Around thirty-seven years, it is closer to 50%, and over thirty-eight years, perhaps 30% of embryos are euploid. Each euploid embryo has an 80% chance for implantation.
So, considering the math above, you can see why we really like to have at least twenty eggs frozen for there to be a good chance to have a baby.
It’s possible to quantify your personal expectation for whether or not you can generate twenty eggs. This is done through ovarian reserve testing. There are two accurate ways to do this.
One is an antral follicle count. This is a transvaginal ultrasound where they count the number of resting small follicles. The “normal” number has been changing in recent years, as ultrasound technology has improved; we keep finding more and more antral follicles. But, in general, you would like to have an AFC of at least twenty.
The other way is AMH testing, which some argue is more accurate. With this test as a very rough guide, you can take the number as expressed in pmol/L and divide by 2 to anticipate the number of eggs you might have with stimulation. We like to see AMH levels of 20 pmol/L or higher.
So, you might want to reach out to your doctor to look for an antral follicle count and AMH test if you’re thinking of fertility preservation. With this information, you can personalize whether or not the technology is even really applicable to your situation.
If this is a path you’d like to explore, it would be a good next step to access counselling. Egg freezing is far from a perfect technology, and is not a perfect insurance plan for having a baby. You might want to talk out your alternatives, including achieving pregnancy in the near term (such as with donor sperm, if that were a necessity), versus not taking on the pressure of freezing eggs at all. For many people, this would be a highly emotional decision, but if after counselling and ovarian reserve testing you feel like freezing is right for you, the technology these days well supports this choice.
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