Have you ever wondered about the number of eggs you have and how it changes throughout your life? It’s a common question, especially for those thinking about family planning. Understanding your ovarian reserve—the number and quality of your eggs—can provide valuable insights into your fertility. Let’s break down this complex topic into easy-to-understand information.
The Amazing Egg Story
Did you know that you have the most eggs you’ll ever have before you are even born? Around five to seven months into fetal development, a female fetus has about 6 million eggs!
From fetal development through menopause, the number of eggs declines with age. But only a tiny fraction of these eggs will ever be ovulated.
Here is a look at the natural decline of egg quantity over time:
- At 20 weeks gestation: A female fetus has about 6 to 7 million immature eggs.
- At birth: That number drops to around 1 to 2 million eggs.
- By puberty: A young girl has about 300,000 to 500,000 eggs remaining.
- During the reproductive years: About 5,000 eggs are activated each cycle, but only 1 (sometimes 2) mature and are released through ovulation. The rest are naturally lost.
- By menopause: Fewer than 1,000 eggs typically remain.
💡 Fun fact: Over a woman’s reproductive lifetime, she will ovulate about 400–500 eggs—less than 0.1% of the eggs she was born with.
This natural egg loss, known as atresia, happens continuously from fetal life onward. It is important to understand that the body does not “run out” of eggs because of ovulation alone, because the vast majority are lost through atresia.
“Even though girls are born with roughly 1-2 million egg follicles, only about 300,000 remain by the time their periods begin. And while thousands of eggs are recruited each cycle, most do not survive to ovulation.”
~ Dr. Ruchi Amin
Menstruation and Ovulation
Why don’t we start our periods at birth if we have so many eggs? It’s because these eggs need to mature. Puberty kicks off when the hypothalamus in the brain releases the gonadotropin-releasing hormone (GnRH). This in turn triggers the release of follicle-stimulating hormone (FSH) and luteinizing hormone (LH), which are essential for egg development and ovulation.
How Ovulation Works
Every month, your ovaries select hundreds of potential eggs for development. FSH helps these fluid-filled sacs, called follicles, grow. However, only one egg typically matures and releases during ovulation, thanks to LH. The body reabsorbs the rest. It might seem wasteful, but this is a natural process.
Does Taking Oral Contraceptives Preserve Eggs?
This is a common question—and the short answer is kind of, but not exactly.
Oral contraceptive pills (OCPs) work by preventing ovulation. So while you’re on the pill, you’re not releasing a mature egg each month. This gives your ovaries a bit of a break.
However, here’s the twist: even though ovulation is paused, atresia still happens. In other words, your body continues to naturally lose eggs each cycle, even if none are being ovulated. So while OCPs can reduce the number of eggs lost through ovulation, they don’t stop or significantly slow the overall decline in egg count.
OCPs also cannot pause aging or improve egg quality. Your biological clock continues to tick, and age remains the most important factor for both the quantity and quality of eggs. So while the pill may offer some other protective effects, it isn’t a substitute for fertility preservation options like egg freezing.
⚠️ If you’re considering fertility preservation, speak with a fertility specialist about egg freezing or testing your ovarian reserve.
Age-Related Fertility Changes
As women age, both egg quantity and quality decline. This natural process can affect fertility and the chances of successful pregnancy, even with assisted reproductive technologies.
Here’s a general timeline of age-related fertility milestones:
In Your 20s
- This is typically considered the peak of fertility.
- Women in their early to mid-20s have about a 25–30% chance of conceiving each cycle.
- Egg quality is generally excellent, with lower risks of chromosomal/DNA abnormalities.
In Your 30s
- Fertility begins to decline gradually around age 30.
- Between ages 32 to 35: The decline becomes more noticeable. Egg count is around 120,000, and monthly chances of conception drop to 20%.
- At age 37, there is a sharper decline — egg count may fall to 25,000 or fewer, and quality begins to diminish significantly.
In Your 40s
- By age 40, the chance of natural conception drops to around 5% per cycle.
- Egg quality becomes a major concern. The risk of chromosomal abnormalities (such as Down syndrome) increases, as does the risk of miscarriage.
- By your mid 40’s, fertility treatments like IVF are less likely to succeed using your own eggs, but success rates improve significantly with donor eggs from younger women.
By Menopause (average age 52)
- Fewer than 1,000 eggs remain.
- As egg reserves decline further, the ovaries become less responsive to hormone signals like FSH (follicle-stimulating hormone).
- Estrogen and progesterone levels drop, and menstrual cycles become irregular.
- At this point natural conception is no longer possible.
Why Does Egg Quality Matter?
It’s not just about the number of eggs; it’s about their quality. Each egg carries chromosomes that must divide properly to produce a healthy embryo. As eggs age, the chances of chromosomal errors (like extra or missing chromosomes) increase. This is why the risk of miscarriage and conditions like Down syndrome increases with age.
Factors That Affect Your Egg Reserve
Several factors can influence your egg quantity and quality:
- Age: The biggest factor.
- Genetics: A family history of premature menopause can be a significant indicator.
- Medical Conditions: Endometriosis, polycystic ovary syndrome (PCOS), primary ovarian insufficiency (POI), autoimmune disorders, and cancer treatments can all impact your eggs.
- Lifestyle: Smoking, excessive alcohol, poor diet, and high stress can contribute to oxidative stress, which damages eggs.
- Other Factors: Pelvic surgeries, sexually transmitted infections, and certain genetic conditions like Turner syndrome or Fragile X syndrome.
Can You Test Your Egg Count?
There are a few ways to get an estimate of your ovarian reserve (the number of eggs you have left):
- Antral Follicle Count (AFC): An ultrasound counts the visible follicles in the ovaries. More follicles generally indicate a higher egg reserve.
- AMH Test: Measures anti-Müllerian hormone in your blood, which reflects how many follicles are developing in the ovaries. AMH levels remain stable throughout the menstrual cycle, making this a reliable test all month long.
Keep in mind, though, these tests do not predict your ability to get pregnant—they only give a rough picture of egg quantity, not quality. Factors like genetics, lifestyle, and medical conditions can all influence fertility.
Quick Recap
- A woman is born with all the eggs she will ever have.
- Fewer than 0.1% of those eggs are ever ovulated.
- Egg quality and quantity decline with age, especially after 35.
- Birth control does not stop aging or preserve fertility.
- As age advances, the chances of successful conception decrease.
Closing
Fertility is a deeply personal journey, and understanding how your body’s egg supply changes over time can help you make more informed decisions about family planning. If you’re planning to delay having children or facing fertility challenges, it’s never too early to consult a fertility specialist about your options—whether it’s fertility preservation, assisted reproductive technologies, or simply understanding the changes your body is going through.
Whatever path you choose, knowledge and early preparation can empower you to navigate your fertility journey with confidence.
