A female fetus has the most eggs she will ever have at around 20 weeks of gestation: roughly 6 to 7 million. From that point on, the number only goes down. By birth, it drops to 1 to 2 million, and by puberty, about 300,000 remain. Of those, only around 400 to 500 will ever be released during ovulation across a woman’s reproductive life.
Egg Count Before Birth
Egg cells start forming early in fetal development. By the midpoint of pregnancy, a female fetus carries her lifetime peak of 6 to 7 million immature eggs. But even before birth, the vast majority of those eggs are naturally reabsorbed by the body in a process called atresia. By the time a baby girl is born, only 1 to 2 million eggs remain. This isn’t a sign of anything going wrong. It’s a normal part of development, and 1 to 2 million is still far more than will ever be needed.
From Puberty Through the Reproductive Years
The decline continues through childhood. By the time a girl reaches puberty, roughly 300,000 eggs are left. That sounds like a steep drop from birth, but 300,000 is more than enough for a full reproductive lifespan.
Each menstrual cycle, the ovaries recruit a batch of immature eggs to begin maturing, but typically only one becomes dominant and gets released during ovulation. The rest of that batch break down. This means you lose far more eggs per cycle than the single one you ovulate. Over an entire reproductive life, a woman ovulates approximately 400 to 500 eggs total. The remaining hundreds of thousands are lost gradually through that same natural reabsorption process that began before birth.
By age 30, most women have somewhere around 100,000 to 150,000 eggs remaining. By 35, the pace of decline accelerates noticeably. By 40, the supply is significantly reduced, and by the mid-40s, most women are approaching the threshold where menopause begins.
Why Egg Quality Matters More Than Count
The raw number of eggs remaining is only part of the picture. Egg quality, meaning whether an egg has the correct number of chromosomes, matters just as much for fertility. Chromosomal errors in eggs increase with age, and the rate of increase has a clear inflection point around age 35. Before 35, the rate of the most common type of chromosomal error rises slowly. After 35, it accelerates to more than double that pace.
This is why fertility declines with age even when a woman still has thousands of eggs in reserve. A 25-year-old and a 40-year-old might both have eggs available, but a much higher proportion of the older woman’s eggs will carry chromosomal abnormalities that prevent a healthy pregnancy. These errors are the primary reason miscarriage rates rise and conception rates fall in the late 30s and 40s.
That said, egg count alone doesn’t determine whether you can get pregnant. Sperm quality, uterine health, and fallopian tube function all play significant roles. A low egg count doesn’t mean conception is impossible. You only need one viable egg to become pregnant.
How Doctors Estimate Your Egg Supply
There’s no test that directly counts every egg in your ovaries. Instead, doctors use indirect markers to estimate your ovarian reserve. The most common is a blood test measuring anti-Müllerian hormone (AMH), a protein produced by the small follicles in your ovaries. Higher AMH levels correspond to more remaining eggs, and lower levels suggest fewer.
General AMH reference ranges look like this:
- Average: 1.0 to 3.0 ng/mL
- Low: under 1.0 ng/mL
- Severely low: 0.4 ng/mL
AMH levels decline predictably with age. At 25, a typical level on the lower end is around 3.0 ng/mL. By 30, it’s closer to 2.5. At 35, about 1.5. By 40, around 1.0, and by 45, roughly 0.5. These are lower-end estimates, so many women will test higher than these numbers at any given age.
One important caveat: ovarian reserve tests are most useful for predicting how well you’d respond to fertility treatments like IVF. A low result doesn’t necessarily mean you can’t conceive naturally. It indicates fewer eggs are available, not that the remaining eggs are incapable of producing a pregnancy.
What Happens at Menopause
Menopause occurs when the egg supply is essentially exhausted. The average age of menopause in the United States is 51, but it can happen anywhere from the early 40s to the late 50s. When only about 1,000 eggs remain, hormone levels shift enough that ovulation stops and menstrual cycles end permanently.
Some women experience earlier-than-expected declines. Women who respond very poorly to ovarian stimulation during IVF (producing three or fewer eggs) have a substantially higher risk of entering menopause early compared to women with normal responses.
Can Women Make New Eggs?
For decades, the established view was simple: women are born with all the eggs they’ll ever have, and no new ones are produced after birth. That idea has been partially challenged. In 2004, researchers identified stem cells in mouse ovaries that appeared capable of generating new egg cells. Since then, similar cells have been found in the ovaries of rats, pigs, cows, monkeys, and humans.
The reality, however, is more complicated than the headlines suggest. In mice and rats, these stem cells have produced functional eggs that led to viable offspring. In humans, all research so far has been limited to lab experiments. No one has demonstrated that these stem cells actively produce new eggs inside a living woman’s body. The current evidence suggests that even if these cells exist in human ovaries, they don’t appear to replenish the egg supply on their own under natural conditions. For now, the practical answer remains the same: the eggs you’re born with are the ones you have to work with.
Factors That Affect the Rate of Decline
Genetics is the strongest factor influencing how quickly your egg supply diminishes. If your mother or sisters experienced early menopause, you’re more likely to as well. Certain medical treatments, particularly chemotherapy and pelvic radiation, can damage or destroy eggs and accelerate the timeline significantly.
Smoking is often cited as a factor, and heavy long-term smoking does appear to affect ovarian reserve. Research suggests a threshold effect: women with 10 or more “pack years” of smoking (the equivalent of a pack a day for 10 years) show measurable reductions in AMH levels. Below that threshold, the impact on measurable ovarian reserve markers is not statistically significant, though smoking affects fertility through other pathways including reduced blood flow to reproductive organs and damage to egg DNA.
Ovarian surgery, even for benign cysts, can remove healthy ovarian tissue along with the targeted problem, reducing the remaining egg supply. If you’re facing ovarian surgery and fertility matters to you, it’s worth discussing tissue-sparing techniques with your surgeon beforehand.