The average woman is born with about 2 million eggs. That number drops to roughly 400,000 by puberty and continues declining throughout her reproductive years until about 1,000 remain at menopause, typically around age 51. Of those millions of eggs, only about 400 will ever be released through ovulation during a lifetime.
Egg Count at Every Life Stage
A female fetus actually reaches peak egg count before birth, during the fifth month of pregnancy. From that point forward, the number only goes down. By the time a baby girl is born, she has around 2 million eggs stored in her ovaries. By the time she reaches puberty, that count has already fallen to about 400,000, even though none of those eggs have been ovulated yet.
During the reproductive years (roughly ages 12 to 51), about 1,000 eggs are lost every month. That sounds like a lot, and it is, but only one of those eggs (occasionally two) is actually released for potential fertilization. The rest break down and are reabsorbed by the body through a natural process called atresia. Over a full reproductive lifespan, roughly 250,000 eggs are lost through this process alone. By the time menopause arrives, approximately 1,000 eggs remain, but they are no longer fertile.
Why So Many Eggs Are Lost Each Month
Every menstrual cycle, a group of eggs begins maturing at the same time. These eggs compete for hormonal signals, and typically only one “wins” and gets released during ovulation. The rest of the group, sometimes dozens of eggs, don’t survive. They undergo a programmed cell death that allows the body to quietly reabsorb them without any inflammation or symptoms. This isn’t a malfunction. It’s how the ovaries are designed to work.
This means the vast majority of your eggs will never have a chance at fertilization. Out of the 2 million you started with, only about 400 are ever ovulated. The rest serve as a biological reserve that gradually depletes over time, and the rate of that depletion accelerates after age 35.
What Speeds Up Egg Loss
Some factors can drain your ovarian reserve faster than normal aging would. Chemotherapy and radiation therapy are among the most significant, as they can damage the genetic material inside egg cells. Cigarette smoke is another well-established factor that accelerates egg depletion. Exposure to certain chemicals, pesticides, and even some viral infections may also play a role. Any surgery involving the ovaries, such as removing ovarian cysts, carries a risk of reducing egg count as well.
When the ovaries lose their eggs too early, before age 40, it’s called primary ovarian insufficiency. This condition can cause irregular periods, difficulty conceiving, and early onset of menopausal symptoms. It can happen because of genetic factors, autoimmune conditions, or the environmental exposures mentioned above.
Can Women Make New Eggs?
For decades, the accepted science was straightforward: women are born with all the eggs they’ll ever have, and no new ones are produced after birth. That idea dates back to 1951 and has guided reproductive medicine ever since.
More recently, researchers have identified a rare population of cells in the ovaries of reproductive-age women that share characteristics with egg-producing stem cells found in rodents. This raised the possibility that some degree of new egg production might occur in adults. However, the scientific community remains divided on whether these cells actually contribute to fertility under normal conditions. For now, the practical reality hasn’t changed: your egg supply is finite, and the eggs you have today are the eggs you were born with.
How Doctors Estimate Your Remaining Eggs
There’s no test that can count your exact number of remaining eggs, but two common tests give a useful estimate of your ovarian reserve.
The first is a blood test measuring anti-Müllerian hormone (AMH), a protein produced by the small follicles in your ovaries. Higher levels suggest more eggs remain. A typical AMH level falls between 1.0 and 3.0 ng/mL, while levels under 1.0 ng/mL are considered low and levels at 0.4 ng/mL are severely low. These numbers decline predictably with age: at 25, a lower-end estimate is about 3.0 ng/mL; at 35, it’s around 1.5 ng/mL; and by 40, it drops to about 1.0 ng/mL.
The second test is an antral follicle count, done via ultrasound early in your menstrual cycle. A technician counts the small, resting follicles visible on each ovary. A count of 22 to 35 is considered good and typically predicts a strong response to fertility treatments. A count of 14 to 21 is intermediate and still normal, though responses to fertility drugs can be more variable. These tests are most commonly ordered when someone is exploring fertility treatment options, but they can also give a general sense of reproductive timeline for anyone curious about where they stand.
Age and Egg Quality
Egg count is only part of the picture. Egg quality matters just as much, if not more, for fertility. As eggs age, they become more prone to chromosomal errors during cell division. This is why the risk of miscarriage and chromosomal conditions like Down syndrome increases with maternal age. A 25-year-old has both more eggs and higher-quality eggs than a 40-year-old, which is the main reason fertility declines so significantly in the late 30s and early 40s.
Fertility begins declining gradually around age 32 and drops more sharply after 37. By the early 40s, even with tens of thousands of eggs potentially still present, the proportion of chromosomally normal eggs is much lower. This is why age remains the single strongest predictor of natural conception success, regardless of what any individual test shows.