Choosing an Egg Donor: The Role of Biomarkers

If you're pursuing egg donation to build your family, you’ve probably heard that age matters. However, when it comes to the number of eggs a donor might produce in a single cycle, age is only part of the picture. Fertility doctors use a combination of biological indicators called ovarian reserve markers to get a clearer sense of how a donor is likely to respond to stimulation medication. These markers include AMH (anti-Müllerian hormone), AFC (antral follicle count), and yes, age. Together, they can help predict how many eggs a donor might yield in a given cycle.

Understanding these biomarkers can help you make better decisions: whether that’s about which donor to match with, whether to split a cohort, or whether you may need multiple cycles to meet your family-building goals. This article explains what each of these markers means, how they’re used in donor screening, and what they can (and can’t) tell you about potential outcomes.

Donor AMH: anti-Müllerian hormone

AMH is a hormone released by cells in developing egg follicles. It gives a general sense of a person’s’s ovarian reserve, or the number of eggs they still have. In most people, AMH levels peak in the mid-20s. For intended parents working with an egg donor, a higher AMH level usually suggests the donor has a good chance of responding well to ovarian stimulation, meaning more eggs are retrieved in a single cycle.

That said, there’s a wide range of what’s considered “normal,” and AMH is just one piece of the puzzle. A very high AMH might raise the risk of ovarian hyperstimulation syndrome (OHSS), especially in donors with polycystic ovary syndrome (PCOS). While high AMH may seem appealing at first glance, it still needs to be considered within the broader clinical context. On the other hand, a lower AMH doesn’t necessarily mean a donor isn’t a good candidate, especially if they’re young and have a good antral follicle count.

At Cofertility, an AMH level of at least 2.0 ng/mL is required for our donors. This threshold is based on clinical data suggesting that donors with this level are more likely to have a strong response to fertility medications and produce enough eggs to support both donation and personal use.

AMH is measured through a simple blood test and is often one of the first screening tools used to assess a donor’s fertility potential.

Read more in Does AMH Matter When Choosing an Egg Donor?

Donor AFC: antral follicle count

Antral follicle count is a snapshot of how many follicles are visible on a donor’s ovaries at a particular point in their cycle, usually early in the menstrual cycle, when baseline testing is done. These are the small, fluid-filled sacs that each contain an immature egg. During a stimulation cycle, the follicles grow larger and the eggs inside them mature ,making them available for retrieval.

AFC is measured by transvaginal ultrasound, and it gives a real-time look at the ovaries. The more antral follicles, the higher the potential number of eggs that could be retrieved. In clinical terms, a “normal” AFC is typically somewhere between 10 and 20 follicles (counting both ovaries), but many donors exceed that.

AFC is considered one of the most reliable indicators of ovarian response. While AMH tells you about the pool of follicles available in a more general sense, AFC shows you what’s happening right now. Since AFC is a real-time snapshot of the ovaries, it can fluctuate slightly from month to month, but these variations are typically minor and don’t significantly impact how a donor is expected to respond. For intended parents, a donor with a strong AFC may provide reassurance that the stimulation cycle will likely yield a solid number of mature eggs.

Donor age: still an important piece of the puzzle

You already know age is a factor. But what’s important to understand is that age affects not just the number of eggs a donor may produce, but also the quality of those eggs—specifically, their likelihood of leading to a healthy embryo.

That’s why most egg donation programs set an age range for donors, usually between 21 and 33 years old (we follow these guidelines at Cofertility). While there’s no legal maximum age to become an egg donor, the American Society for Reproductive Medicine (ASRM) recommends that donors be under 34, and most clinics follow that guidance. Our limit accounts for the fact that it can take some time to match with intended parents and complete a cycle, and we want donors to still fall within the recommended age window by the time the cycle takes place.

Within that range, there can still be differences in both quantity and quality of eggs based on things beyond age. 

That said, most donors who get medical clearance respond very well to stimulation and produce excellent-quality eggs, whether in their late 20s and early 30s. Age is just one variable, and when combined with the other biomarkers, it helps doctors build a fuller picture of what to expect from a cycle.

How these markers are used together

No single biomarker tells the whole story. Fertility doctors look at AMH, AFC, and age together to estimate a donor’s likely response to ovarian stimulation. This is sometimes called “ovarian reserve testing,” but the goal isn’t just to count eggs. It’s also to plan appropriately for stimulation protocols and optimize outcomes.

For example, if a donor has high AMH and high AFC, they might be expected to produce 20+ eggs in a cycle, and the care team may start with a lower dose of stimulation medications to reduce the risk of overstimulation. If another donor has AMH on the lower end of the normal range and an average AFC, the team may anticipate a more moderate yield (perhaps 10 to 15 eggs) and plan accordingly by using a higher starting dose of medications to optimize their response to treatment.

Limits of prediction

While AMH and AFC are helpful, they’re not crystal balls. A donor with stellar biomarkers could still have a retrieval cycle that yields fewer mature eggs than expected. Likewise, a donor with average numbers might surprise everyone with a strong response.

Biology isn’t always predictable, and cycle outcomes can vary even in the same donor across multiple cycles. That’s why experienced clinics combine biomarker data with close monitoring during the stimulation phase to make adjustments in real time.

It’s also worth noting that the number of eggs retrieved isn’t the only metric that matters. Fertilization rate, embryo development, and success rates with IVF transfer all depend on additional factors,some of which can’t be measured ahead of time.

What this means for you as an intended parent

As you look through donor profiles, you may see some numbers directly—such as AMH or age—or you might get a broader summary from your clinic about the donor’s reproductive potential. It’s a good idea to ask your doctor what these biomarkers might suggest about how many eggs the donor is likely to produce, and how that aligns with your goals.

That said, it’s important to understand that every donor listed has already cleared a rigorous screening process. Fewer than 5% of applicants are accepted into Cofertility’s egg sharing program. If a donor has made it through, it means our medical advisors (who are board-certified reproductive endocrinologists) have reviewed their health, biomarkers, and ovarian reserve, and determined if they’re likely to respond well to treatment.

Within this highly qualified group, small differences in biomarker levels may not translate to big differences in actual outcomes. Rather than fixating on a slightly higher AMH or AFC, it may be more helpful to focus on which donor feels like the right match for your family, whether that’s based on their background, values, personality, or something less tangible that just clicks for you.

The bottom line

AMH, AFC, and age can offer helpful insight into how many eggs a donor may produce and how your doctor will approach their care during the cycle. These biomarkers are useful tools for setting expectations and guiding decisions, but they’re not guarantees.

All egg donation involves some level of uncertainty, even with strong indicators. That’s why programs like Cofertility set high standards up front. This ensures that every donor in the pool has a solid chance of success. Once a donor is approved, the differences between candidates tend to narrow, and the best choice is often the one that feels most aligned with your values and goals—not just the numbers.

Ask questions, gather information, and talk with your care team. But don’t be afraid to trust your gut, too. The right match will meet both the medical criteria and feel like someone who could help you build the family you’ve been hoping for.

Read more:

• Why Egg Donor Age Matters (And Why It Doesn't)
• Does AMH Matter When Choosing an Egg Donor?
• Will My Baby Look Like Me If I Use an Egg Donor?
• Shared vs. Separate Egg Donor Cycles: A Guide for Gay Dads

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