A woman at age 25 has roughly 100,000 to 300,000 eggs remaining in her ovaries. That sounds like an enormous number, but it represents a sharp drop from what she started with. The vast majority of eggs are lost naturally through a process called atresia, where immature eggs break down and get reabsorbed by the body, long before they ever have a chance to be ovulated.
How Egg Count Changes From Birth to 25
A baby girl is born with all the eggs she will ever have, typically between 1 million and 2 million. Unlike sperm, which men produce continuously, eggs are a finite resource set at birth. From that point forward, the number only goes down.
By puberty, around age 12, the count has already fallen to roughly 300,000 to 500,000. Most of that loss happens without any outward sign. Each month after puberty begins, a batch of immature eggs starts developing, but only one (occasionally two) matures enough to be released during ovulation. The rest of that batch degrades. By the mid-20s, somewhere around 100,000 to 300,000 eggs remain. The decline is steady but not linear: it accelerates significantly after age 35.
Why 25 Is Considered a Fertility Sweet Spot
Egg count is only half the picture. Egg quality, meaning whether an egg carries the correct number of chromosomes, matters just as much for conception and healthy pregnancy. At 25, both quantity and quality are near their best. A woman in her early to mid-20s has a 25 to 30 percent chance of getting pregnant during any given menstrual cycle, which is about as high as natural conception odds get.
Interestingly, the very youngest adults don’t have the absolute lowest rates of chromosomal abnormalities in their eggs. A large review of over 15,000 embryo biopsies found that women 23 and under actually had a slightly elevated rate of chromosomal errors, with more than 40 percent of embryos testing abnormal. The lowest risk window was between ages 26 and 30. After 30, the rate of abnormal eggs climbs steadily, becoming a major factor in miscarriage and difficulty conceiving by the late 30s and 40s.
How Doctors Measure Ovarian Reserve
If you’re curious about your own egg supply, doctors can estimate it using a blood test that measures Anti-Müllerian Hormone (AMH). AMH is produced by the small follicles in your ovaries that contain developing eggs, so higher levels generally indicate a larger remaining pool. For a 25-year-old, an AMH of around 3.0 ng/mL is typical, though the general “average” range spans from 1.0 to 3.0 ng/mL across reproductive age. A result below 1.0 ng/mL at 25 could signal a lower-than-expected reserve, sometimes called diminished ovarian reserve.
It’s worth noting that AMH reflects quantity, not quality. A normal AMH level doesn’t guarantee that your eggs are chromosomally healthy, and a lower AMH doesn’t necessarily mean the eggs you do have are poor quality. The two measures are largely independent, which is why age remains the single best predictor of overall fertility.
What Can Affect Your Egg Count
The number of eggs you lose over time is largely determined by genetics. Some women naturally start with a larger pool; others start with fewer. But one confirmed lifestyle factor speeds up the loss: smoking. According to the American Society of Reproductive Medicine, tobacco use is the only lifestyle factor directly associated with decreased ovarian reserve. Smoking damages the ovaries in ways that reduce the total egg count, not just egg quality, and the effect is dose-dependent, meaning heavier smokers face greater losses.
Other lifestyle factors like diet, exercise, and body weight influence egg quality but don’t appear to change how many eggs you have. Maintaining a healthy weight and avoiding tobacco are the most practical steps for protecting both the quantity and health of your remaining eggs. Certain medical treatments, particularly some chemotherapy drugs and ovarian surgery, can also reduce egg count significantly, but these are clinical situations rather than everyday lifestyle choices.
What These Numbers Mean in Practice
Having 100,000 or more eggs at 25 might seem like an unlimited supply, but only about 400 to 500 eggs will ever actually be ovulated across your entire reproductive life. The rest are lost to natural attrition. The key takeaway is that at 25, time is on your side in two ways: you still have a large reserve, and the eggs you’re ovulating are more likely to be chromosomally normal than they will be in later years.
That said, egg count varies widely between individuals of the same age. Two 25-year-olds can have very different ovarian reserves based on genetics alone. If you’re planning for the future and want a clearer picture of where you stand, an AMH test paired with an ultrasound to count visible follicles can give you a personalized estimate rather than relying on population averages.