Did You Know? Your Eggs Have “Grades” Too! — Understanding GV, MI, and MII Stages

When it comes to IVF (in vitro fertilization), many people have heard about embryo grading — terms like “3AA” or “4BB” that describe embryo quality. But before an embryo even forms, the egg itself also has different maturity levels or “grades.”

The maturity and quality of an egg play a critical role in determining whether fertilization will occur and how well the embryo develops afterward.

Today, let’s explore what those common labels — GV, MI, and MII — actually mean, and why they matter for your IVF journey.

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1. From Immature to Mature: The Three Stages of an Egg

Not all eggs retrieved during an IVF cycle are at the same stage of development. Under the microscope, eggs are classified into three main maturity stages based on how far they’ve progressed through cell division:

1. GV Stage (Germinal Vesicle)

   
   

   This is the immature stage. The egg still contains a visible nucleus, known as the “germinal vesicle.” GV eggs are not yet ready to be fertilized and therefore cannot be used in IVF.

   
   

2. MI Stage (Metaphase I)

   
   

   This is the intermediate or in-between stage. The egg is in the process of maturing and undergoing the first meiotic division but hasn’t completed it yet. MI eggs may sometimes continue to mature in the lab through a process called in vitro maturation (IVM), but their success rates and developmental potential are generally lower than fully mature eggs.

3. MII Stage (Metaphase II)

   
   

   This is the fully mature stage — exactly what we want for fertilization. Under the microscope, an MII egg has released its first polar body, meaning it has completed the first meiotic division and is ready to combine with sperm.

   
   

   Only MII eggs can be fertilized normally (via IVF or ICSI).

2. Why Egg Maturity Matters

Egg maturity determines whether fertilization can take place and how viable the resulting embryo will be.

• GV eggs → Cannot be fertilized

• MI eggs → May mature in the lab, but with limited success

• MII eggs → Ready for fertilization and capable of developing into healthy embryos

In a typical IVF cycle, about 70–85% of retrieved eggs reach the MII stage, although this rate varies depending on age, ovarian response, medication protocol, and individual biology.

3. Egg Grade vs. Embryo Quality

While it’s true that “good embryos come from good eggs,” not every mature (MII) egg will necessarily form a high-quality embryo. Egg quality also depends on other factors such as chromosomal integrity, energy metabolism, and cellular structure.

Your fertility team evaluates the maturity and overall performance of your eggs, fertilization rates, and embryo growth to better understand your egg quality and to tailor your next treatment plan if needed.

4. Can Immature Eggs Still Be Used?

In some cases, MI or even GV eggs can be cultured in the lab to allow them to mature — a technique known as in vitro maturation (IVM).However, IVM is still considered an adjunct approach, as lab-matured eggs generally have a lower fertilization and developmental potential compared to naturally matured MII eggs.

Your doctor will determine whether IVM is a suitable option based on your individual case.

✨ Final Thoughts

In IVF, it’s not just about how many eggs are retrieved — what truly matters is how many of them are mature (MII) and ready for fertilization.

Understanding egg grading helps you make sense of your retrieval report and gives you a clearer picture of what’s happening behind the scenes in the lab.

🌸 Every mature egg represents a new possibility. By learning more about your eggs, you’re one step closer to understanding — and achieving — your dream of a healthy pregnancy. 💕