A woman is born with about one million eggs, but only around 300,000 remain by puberty, and just 400 to 500 of those will ever be released through ovulation during her reproductive years. By the time menopause arrives, fewer than 1,000 eggs typically remain. The vast majority of eggs are lost not through ovulation but through a natural process called atresia, where the body reabsorbs unused follicles every month.
Egg Count From Birth to Menopause
The number of eggs a woman has is fixed before she’s even born. During fetal development, the ovaries contain their peak supply of egg cells. At birth, roughly one million follicles (each containing an immature egg) are present. That number drops steadily through childhood without any hormonal trigger, reaching about 300,000 by puberty.
From puberty onward, the decline accelerates. Each month, a group of up to 50 follicles begins developing in response to hormonal signals. Only one of those follicles typically becomes dominant and releases a mature egg during ovulation. The rest break down and are reabsorbed by the body. This means that for every single egg ovulated, dozens are lost. Over a full reproductive lifetime, roughly 400 to 500 eggs make it to ovulation. The other 299,500 or so are lost to atresia.
The rate of loss isn’t constant. It picks up noticeably after age 35, and by the time a woman reaches menopause (around age 50 on average), fewer than 1,000 eggs remain. Those remaining eggs are generally lower in quality, which is a separate but equally important factor in fertility.
Egg Quantity vs. Egg Quality
Having a large number of eggs doesn’t guarantee fertility, and having a lower count doesn’t necessarily prevent pregnancy. Egg quality matters just as much as quantity, and quality declines with age in ways that numbers alone don’t capture. Older eggs are more likely to have chromosomal abnormalities, which increases the risk of miscarriage and makes conception harder.
This distinction shows up clearly in IVF outcomes. For women under 35, retrieving around 9 eggs gives a good statistical chance of achieving a live birth. For women between 38 and 40, that number jumps to roughly 18 eggs needed for the same probability. The difference isn’t just about having fewer eggs to work with. It reflects the fact that a smaller percentage of those eggs will be chromosomally normal and capable of developing into a healthy pregnancy.
How Ovarian Reserve Is Measured
If you’re curious about your own egg supply, two tests are commonly used to estimate what doctors call “ovarian reserve.” Neither tells you exactly how many eggs you have, but both give a useful snapshot of where you stand relative to your age group.
AMH (Anti-Müllerian Hormone): This is a simple blood test that can be done on any day of your cycle. AMH is produced by the small follicles in your ovaries, so the level reflects how many developing follicles are present. Typical ranges shift with age: women in their early 20s average 4.0 to 6.8 ng/mL, while women aged 36 to 40 typically fall between 1.0 and 3.5 ng/mL. By ages 41 to 45, the average drops to 0.5 to 1.5 ng/mL.
Antral Follicle Count (AFC): This is an ultrasound done early in the menstrual cycle that counts the small, visible follicles in both ovaries. Women in their early 20s typically have 12 to 30 antral follicles, while women aged 35 to 40 usually have 10 to 15. After 45, the count often drops to 0 to 3. Women with polycystic ovary syndrome (PCOS) can have unusually high counts because the condition causes an increase in small antral follicles.
One important caveat: these markers predict how your ovaries would respond to fertility medications, but they don’t reliably predict your chances of conceiving naturally. Two large studies found that women with low AMH levels (below 0.7 or 1.0 ng/mL) had similar rates of natural pregnancy over 6 to 12 months compared to women with normal levels.
What Speeds Up Egg Loss
Age is the biggest driver of declining ovarian reserve, and no intervention can stop or reverse that process. However, certain factors can accelerate the timeline. Smoking is the only lifestyle factor with clear evidence linking it to faster egg depletion. The American Society of Reproductive Medicine identifies tobacco use as the single modifiable risk factor for decreased ovarian reserve.
Medical causes of accelerated loss include radiation therapy and chemotherapy, ovarian surgery (particularly procedures that remove ovarian tissue), the loss of one or both ovaries, autoimmune conditions, and genetic disorders affecting the X chromosome. For some women, ovarian reserve drops faster than expected without any identifiable cause.
Does Birth Control Preserve Eggs?
A common belief is that hormonal birth control “saves” eggs by preventing ovulation, effectively pausing the biological clock. This isn’t how it works. While the pill does suppress ovulation, atresia continues in the background regardless. Your ovaries keep losing follicles every month whether or not you’re ovulating.
Hormonal contraceptives do temporarily lower the markers used to measure ovarian reserve. A study of 833 women found that AMH levels were 19% lower and antral follicle counts were 16% lower in pill users compared to non-users. But this suppressive effect is temporary. Once the pill is stopped, ovarian function resumes, and the measurements return to their expected range. The pill doesn’t damage your reserve or protect it. It simply masks the readings while you’re on it, which is worth knowing if you’re planning to have your fertility tested.
Practical Takeaways by Age
Your egg supply follows a predictable curve, but individual variation is significant. Two women the same age can have very different ovarian reserves depending on genetics, health history, and lifestyle. Here’s a general framework:
- Under 30: Egg quantity and quality are typically at their highest. AMH levels generally range from 3.0 to 6.8 ng/mL, and antral follicle counts are usually 12 to 30.
- 30 to 35: Reserve is still good but declining gradually. Quality begins to decrease, though the shift is modest at this stage.
- 35 to 40: The rate of egg loss increases noticeably. Both quantity and quality drop more steeply, which is why fertility specialists often emphasize 35 as a meaningful threshold for family planning conversations.
- Over 40: Ovarian reserve is significantly reduced, with AMH levels often below 1.5 ng/mL and antral follicle counts in the single digits. The percentage of chromosomally normal eggs is lower, making both natural conception and IVF more challenging per cycle.
If you’re considering egg freezing or fertility treatment, age at the time of freezing or retrieval matters more than age at the time you eventually try to conceive. The eggs retain the quality they had when they were collected, which is why earlier freezing yields better outcomes per egg.