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Egg cells under a microscope

In the world of reproductive health and fertility, there is a growing interest in understanding the quantity of eggs a woman has, also known as ovarian reserve. The concept of measuring ovarian reserve has gained popularity as more people seek to assess their fertility potential and make informed decisions about family planning. 

But can you truly measure how many eggs you have? Let's delve into the world of ovarian reserve testing and explore the possibilities and limitations.

How many eggs do females have?

Females are born with approximately one to two million oocytes, and it only goes down from here since no new eggs are made. But here's where it gets interesting.

Once we reach puberty, a process triggered by a complex interplay of hormones, only about 300,000 of these oocytes will remain. These precious few will have the opportunity to mature and potentially be released as eggs during our reproductive years. Our bodies typically release just one egg per menstrual cycle, and this process occurs approximately 400 times throughout our lifetime.

These remaining oocytes are not merely passive bystanders. Each one resides within a protective structure called a follicle, where it lies dormant and suspended in the middle of a cell division. Remarkably, the lifespan of an egg is one of the longest among the body's cells. However, this extended duration can also increase the chances of damage and genetic abnormalities as we age.

At menopause, which is defined as one year after your last menstrual period, the pool of remaining oocytes steadily declines until none remain. This natural process signifies the end of our reproductive years.

Understanding the intricacies of egg development and the limited supply available underscores the importance of considering fertility and family planning at an earlier age. Each egg is a precious resource, and its quality and viability can impact the chances of achieving a successful pregnancy. Exploring fertility preservation options, such as egg freezing, can provide women with greater control over their reproductive future.

While the numbers presented here provide a general understanding, it's crucial to remember that everyone’s ovarian reserve is unique. Factors like genetics, lifestyle, and overall health can influence the rate of egg loss and fertility potential. 

Egg count and age

As stated above, females are born with one to two million eggs. By puberty, only about 300,000 of these oocytes will remain. After starting the menstrual cycle, we lose about 1,000 immature eggs every month… meaning by age 37 there are around 25,000 eggs remaining. And by menopause, no more eggs remain.

Here is a rough chart of what this could look like for an individual. Keep in mind that everyone starts with a different number of eggs, and everyone’s rate of decline varies. This chart is just to give you an idea of what this egg count could look like: 

Measuring egg reserve (aka ovarian reserve)

Ovarian reserve refers to the number of eggs remaining in a woman's ovaries at a given time. It is one indicator of a woman's reproductive health, and can help guide fertility treatment decisions. The idea of quantifying ovarian reserve has gained significance as women strive to gain insights into their fertility and make proactive choices about their reproductive journey. And at the same time, at-home tests make it easier to measure your ovarian reserve.

Keep in mind that the number of eggs you have does not necessarily equate to your ability to conceive. Other factors, such as egg quality, the presence of any reproductive disorders, and the overall health of the reproductive system, play significant roles in fertility. Not to mention the health of the sperm! Some people have lower ovarian reserve but still achieve successful pregnancies, while others with a seemingly healthy ovarian reserve may face challenges in conceiving.

How to measure ovarian reserve

One of the most commonly used methods to measure ovarian reserve is through a blood test that evaluates specific hormone levels. These hormones include anti-Müllerian hormone (AMH), follicle-stimulating hormone (FSH), and estradiol. AMH, in particular, has emerged as a reliable marker of ovarian reserve, as it reflects the number of small follicles in the ovaries that contain immature eggs. Low levels of AMH may indicate a diminished ovarian reserve, while higher levels may suggest a larger pool of eggs.

While ovarian reserve testing provides valuable insights, it is not a crystal ball that can predict fertility outcomes with absolute certainty. Ovarian reserve is just one piece of the fertility puzzle, and other factors such as egg quality, uterine health, and sperm quality also play crucial roles in the conception process. Additionally, fertility is influenced by various external factors, including age, lifestyle, and underlying health conditions.

Fertility testing can provide a snapshot of ovarian reserve at a specific moment in time. Ovarian reserve naturally declines with age, and the number of eggs available for fertilization decreases over time. Therefore, it's crucial to interpret the results in the context of your age and overall health.

Egg reserve testing methods

Another consideration when evaluating ovarian reserve is the variation in testing methods and reference ranges used by different laboratories. Each laboratory may have its own set of standards and measurements, which can lead to variations in results. You may want to consult with a fertility doctor who is knowledgeable in reproductive medicine to interpret the test results accurately and provide personalized guidance (if you work with Cofertility, we can help you set this up).

So, can you measure exactly how many eggs you have?

While ovarian reserve testing can provide valuable information, determining the exact number of eggs a woman has remaining in the ovaries is not possible. 

Why? First of all, the number of eggs in the ovaries is not static but rather dynamic and constantly changing. We are born with a finite number of eggs, and this number gradually declines over time through a process called follicular atresia. This natural process of egg loss occurs throughout our reproductive years, and the rate of decline varies from person to person.

Second, the accuracy of measuring the exact number of eggs is hindered by the limitations of current medical technology. While imaging techniques like ultrasound can visualize the presence of ovarian follicles, they cannot precisely determine the number of eggs within each follicle. Additionally, even if the number of follicles can be counted, it does not equate to the exact number of eggs, as not all follicles contain a viable egg.

Ovarian reserve is just one piece of the puzzle

While ovarian reserve testing can provide valuable information, it is just one tool in the broader landscape of fertility assessment. A fertility doctor can consider your medical history, conduct a physical examination, measure your antral follicle count, and may recommend additional tests or imaging studies to provide a comprehensive assessment of your reproductive potential.

Cofertility is a human-first fertility ecosystem rewriting the egg freezing experience. With our Freeze by Co platform, women can freeze their eggs for free when they donate half of the retrieved eggs to a family who can’t otherwise conceive. We are obsessed with improving the family-building journey — today or in the future — and are in an endless pursuit to make these experiences more positive.