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How Do I Know If The Eggs I Froze Are “Good”?

Written in Partnership with Dr. Brooke Hodes-Wertz, NYU Fertility Center

It is not uncommon to hear your doctor talk about “egg quality”. If you have frozen your eggs, you have likely heard that egg quality decreases with age and varies from person to person. When we characterize eggs as “good”, we usually are referring to the number of chromosomes the egg contains. As a woman gets older, her eggs have a harder time maintaining the correct number of chromosomes when combining with sperm. However, even in young, healthy women, all of the eggs they make are not necessarily “good” (i.e., chromosomally normal). So, how can you be reassured that you froze some “good” eggs?

Currently, there is no great way to figure out which eggs are chromosomally normal. Well, at least, not when you freeze them. However, once an embryo is created (meaning that the egg is combined with sperm), the number of chromosomes the embryo contains can be assessed. In the past several years, the technology has rapidly advanced in both the technique used to collect cells from the embryo and the method used to test them.

Today, when women return for their eggs, they will have the option of testing the embryo after the eggs are mixed with sperm and typically grown in culture for five days. Depending on which fertility center is used, this will either involve a fresh embryo transfer the following day, or require embryos to be frozen. By doing this, women can avoid transferring an embryo that contains the incorrect number of chromosomes, which often either do not implant or lead to miscarriage.

Not only can an embryo be tested for the number of chromosomes, but specific genetic disease can be identified. Both egg freezing procedures and comprehensive genetic testing are becoming more and more popular as the technology becomes more available and affordable. This increase in information will lead to more women having a better understanding of their genetic makeup and give them the ability to screen their embryos before transferring them into the uterus, thus preventing the passing of significant genes (such as the BRCA) onto their children.

The best way for a woman to estimate how many of her eggs are normal is to look at her age at the time the eggs are frozen. For example, 50-60% of embryos in a 35-year-old woman will have the correct number of chromosomes. However, that number decreases significantly with age. This attrition is the reasoning behind getting more than one egg from a patient at one time.
It is also important to remember that having the right number of chromosomes is just one component of embryo potential and that “normal” embryos don’t necessarily always implant and make a baby.
So for now, let your frozen eggs chill. When it comes time to return for them, you can let life circumstances shape your plans.

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