As a previous IVF lab director and embryologist, I was often faced with calling patients after their egg retrieval egg freezing cycle. When I called patients they really wanted to know how many eggs and what their egg quality was. And I was quite limited with limited methods into what I could actually tell the patient regarding their egg quality.

Assessing egg maturity status

After retrieval, embryologists first determine whether each egg is mature enough to be frozen. Maturity refers to the developmental stage the egg has reached, whether it's biologically ready to be fertilized. The most important stage is called metaphase II (M2), which simply means the egg has completed a key step in its development. Embryologists can identify this by looking for a small structure called a polar body that has been pushed out of the egg, a visible sign that the egg is mature. Eggs that have not reached M2 yet, known as metaphase I (M1) or germinal vesicle (GV) eggs, are considered immature and are typically not frozen, since they are not yet at the stage where fertilization is possible.

Undergoing vitrification

Once mature eggs are identified, they're preserved through a process called vitrification. This hits the pause button at the current biological age of the eggs. You're not just preserving eggs, you're preserving a moment in time. For example, a 28-year-old who freezes eggs today and uses them at 35 is working with the eggs of a 28-year-old.

Visible differences between eggs

After determining maturity, embryologists observe eggs under a microscope and may notice differences in how eggs look. This can include dysmorphisms, structural differences, and physical features that appear unusual. These visible differences may suggest variation between eggs, but historically they have not reliably predicted outcomes.

Why egg quality has been difficult to define

Egg quality is discussed constantly in fertility care, but there's no strict clinical definition. Providers hold varying definitions for egg quality, and one such definition was described by Dr. Dan Nayot as “The egg’s potential to become a baby.” This potential matters as higher-quality eggs are more likely to fertilize, develop into chromosomally normal embryos, lead to successful pregnancy, and ultimately result in a baby.

Historically, clinics have not had a reliable test to measure egg quality. There is no blood test, ultrasound, or standard clinical test that can determine whether egg quality is average, good, or poor. Tests like AMH or follicle count measure egg quantity, not egg quality.

Age-based statistics: After an egg freezing cycle, most patients leave with two numbers: their age and how many mature eggs were frozen. Some clinics may also use online calculators to estimate live birth potential based on those numbers. However, as Jullin explains, this creates limitations on the assumption that every patient with the same age and egg count will have the same outcome. In actuality, two patients who are both 35 years old with 15 eggs may have the same calculation estimate but different true potential.
Egg variation: One thing patients often don’t realize is that eggs from the same retrieval cycle are not all the same. Even if they were retrieved from the same person, on the same day, each egg is still biologically unique. Some may have stronger developmental potential than others, and historically there wasn’t a reliable way to understand those differences. That variation between eggs can play a major role in future outcomes, and it’s why more personalized insights can be helpful.

AI is changing what embryologists can evaluate

Newer AI technology can now analyze images of frozen eggs down to the pixel level.

It can detect tiny details, patterns, combinations of dysmorphisms, and features embryologists may not consistently identify on their own through tools like Violet. These images are captured while embryologists are already routinely observing eggs after retrieval, so patients do not need any additional procedures.

AI-driven assessments can now provide more personalized predictions about egg thaw survival blastocyst development, chromosomally normal embryos, and personalized chances of live birth

Rather than leaving with just a number of eggs, patients may now receive more individualized insight into the eggs they’ve frozen.

Jullin Fjeldstad, VP of Clinical Embryology & Scientific Operations at Future Fertility, holds a BSc in Biology from the University of Victoria and an MSc in Clinical Embryology from the University of Leeds, UK. With over a decade of experience in the lab, she began her career in 2007 at the Victoria Fertility Centre, quickly progressing to senior embryologist and laboratory director. She now focuses on the clinical implementation of Future Fertility's innovative AI-based tools, scientific collaborations, and sharing research at international fertility conferences.