What Egg Quality Means—And How It Affects Egg Freezing

If you’re thinking about freezing your eggs, you’ve probably heard about the concept of “egg quality.” Maybe a friend mentioned it, or your doctor brought it up during a consultation. It’s one of those fertility buzzwords that can feel vague and hard to pin down. What does “egg quality” actually mean? And more importantly, is there a way to find out what yours is?

Egg quality refers to how likely an egg is to result in a healthy embryo and, eventually, a live birth. It’s not something we can measure directly—there’s no perfect test or score that tells you how “good” your eggs are. But we do have tools to assess your fertility potential, and there are signs and indicators that can give us insight into how your body is responding.

In this article, we’ll walk through what egg quality really means, why it matters, how it changes over time, and the testing options available today. We'll also talk about what to consider when thinking about fertility preservation—and how Cofertility can support you in taking next steps.

What we mean by “egg quality”

In medical terms, egg quality refers to the genetic and cellular health of an egg. A high-quality egg is one that has the right number of chromosomes and is capable of being fertilized, developing into a healthy embryo, and implanting in the uterus.

Eggs with abnormal numbers of chromosomes—called “aneuploid” eggs—are less likely to lead to a successful pregnancy. These eggs may not fertilize, may result in failed embryo development, or may lead to miscarriage if implantation does occur. In some cases, chromosomal abnormalities that originate in the egg can carry through to a developing embryo and lead to a live birth with a genetic condition. Down syndrome (Trisomy 21) is the most widely known example of this, but there are many other conditions that can arise from chromosomal abnormalities. This is why egg quality plays such a big role in fertility, even for people who are ovulating regularly or who feel perfectly healthy.

Unfortunately, there’s no simple blood test or ultrasound that can tell us with certainty which of your eggs are chromosomally normal. Egg quality can only truly be confirmed by creating embryos and performing genetic testing on them, which isn’t part of the typical egg freezing process. But there are other ways to estimate your fertility potential.

Age matters most

Of all the factors that impact egg quality, age is by far the most significant. People with ovaries are born with all the eggs they’ll ever have, and both egg quantity and quality decline over time.

Most people see a gradual decline starting in their early 30s, with a more noticeable drop-off around age 35. By age 40, a higher percentage of eggs are likely to be genetically abnormal. That doesn’t mean you can’t get pregnant or that all your eggs are “bad”—but it does mean fewer of your eggs may be capable of resulting in a live birth.

To put this age-related decline into perspective, here’s what the numbers actually look like:

• At age 25, approximately 20-25% of eggs may be chromosomally abnormal.
• At age 35, this increases to about 40-50%
• At age 40, that figure is up to roughly 70-80%
• At age 43, over 90% of eggs may be chromosomally abnormal

Egg quality is the main reason that IVF success rates drop with age, and why freezing your eggs earlier can increase your odds of having more usable eggs down the road.

Egg quantity vs. egg quality

It’s easy to confuse egg quantity with egg quality, especially since both tend to decline together. But they’re not the same thing.

Egg quantity refers to the number of eggs you have left—your “ovarian reserve.” The most commonly used tests to assess this are AMH (anti-Müllerian hormone) and antral follicle count, which can give us insight into your egg supply. These tests are useful for predicting how many eggs you might produce during a stimulation cycle, which is helpful when planning for egg freezing or IVF.

But these tests don’t tell us anything definitive about the quality of your eggs. It’s entirely possible to have a high AMH and still have a higher percentage of chromosomally abnormal eggs. On the flip side, someone with low ovarian reserve may still have good-quality eggs—it just may take more cycles to find them.

Can you test your egg quality?

Here’s where it gets tricky. There is no test that gives a direct readout of egg quality unless you’re creating and doing genetic testing on embryos. But here are some of the indirect ways we can get clues:

Age

As mentioned, this is the strongest predictor of egg quality. Most fertility specialists use age as a starting point when estimating how many eggs you may want to freeze for a future pregnancy.

Embryo development (in IVF)

If you go through IVF and fertilize your eggs, you can get information about how well your eggs developed into embryos. Some embryos can be biopsied and tested (PGT-A) to check for chromosomal normalcy. This gives a more direct window into egg quality—but it’s not part of standard egg freezing.

Ovarian reserve testing

While it doesn’t tell us about quality, ovarian reserve testing (AMH, FSH, AFC) gives us an idea of your egg quantity. If your numbers are unexpectedly low for your age, it may be worth exploring your optionsmore quickly, especially if you’re considering freezing your eggs.

Cycle response

If you go through an egg freezing cycle, how your body responds to stimulation medications (how many eggs mature, hormone levels during the cycle, etc.) can also offer insight. At Cofertility, we support you through every part of the cycle and help explain what your results might mean.

What affects egg quality besides age?

While age is the biggest factor, other things can also impact egg quality over time. Some are within your control, others aren’t.

• Smoking, whether that’s nicotine or marijuana, is consistently linked to lower egg quality and earlier menopause.
  
  
• Certain medical conditions, like PCOS, endometriosis, or autoimmune disorders, may affect egg health.
  
  
• Chemotherapy or radiation treatments can damage eggs or reduce ovarian reserve.
  
  
• Environmental exposures to endocrine-disrupting chemicals may play a role, although research is still ongoing.
  
  

There's growing interest in how lifestyle, diet, and supplements may support egg health. While there's no magic food or pill that guarantees higher-quality eggs, taking care of your overall health—getting enough sleep, avoiding smoking, managing stress, and maintaining a balanced diet—can support your fertility.

How Cofertility can help

If you’re thinking about freezing your eggs, understanding your fertility is the best place to start. At Cofertility, we’re here to guide you through the process with clarity and support—not pressure.

Through our Split and Keep programs, we offer egg freezing in a way that puts you in control:

• With our Split Program, you can freeze your eggs for free when you donate half to a family who can’t otherwise conceive. This model attracts people motivated by shared values—not just financial incentives—and gives donors a way to preserve their own fertility without the high cost.
  
  
• Our Keep Program is designed for those who want to freeze and keep all of their eggs. We help you navigate the process, connect you with partner clinics, and offer a support team to answer your questions at every step.
  

Our team includes experienced nurses (like me), fertility doctors, and donor coordinators who are here to help you feel informed—not overwhelmed. Whether you're ready to move forward or just want to ask questions, we’re here when you’re ready.

Final thoughts

There’s a lot of noise out there about egg quality—and it can be hard to separate fact from fear. While there’s no single test to measure it, your age, hormone levels, and cycle response can all offer clues. If you’re curious about your fertility, or planning ahead for the future, taking steps to learn more now can give you more options later.

Freezing your eggs isn’t the right decision for everyone. But if you’re considering it, Cofertility can help you do it in a way that’s empowering, transparent, and supported by people who care.

You deserve to make these decisions with clarity and confidence—not confusion. Let us help you get there.