How Many Viable Eggs Does a Woman Have by Age?

A woman is born with all the eggs she will ever have, and the number drops steadily from that point forward. The rough figures most reproductive endocrinologists cite are about one to two million at birth, around 300,000 to 500,000 at puberty, and somewhere in the low thousands by the late thirties and early forties. But the raw count tells only part of the story, because the proportion of those remaining eggs that can produce a healthy pregnancy also falls with age, and that decline in quality is what drives most of the fertility challenges women face after their mid-thirties.

How the Numbers Change From Birth to Menopause

The peak actually happens before birth. During fetal development, the ovaries contain millions of immature egg cells called oocytes. Most of these are lost through a natural process of cell death long before a girl reaches puberty, leaving a starting pool of a few hundred thousand. From puberty onward, a batch of follicles begins maturing each menstrual cycle, but typically only one egg is released at ovulation. The rest of that batch degrades. Over about 35 to 40 years of reproductive life, roughly 400 to 500 eggs will actually ovulate. The remaining hundreds of thousands are reabsorbed by the body.

The rate of loss is not constant. It stays relatively gradual through the twenties and early thirties, then accelerates. By the late thirties, most women have noticeably fewer follicles available each cycle, and by the early forties, the pool has thinned enough that cycles become less regular. Menopause occurs when the supply is essentially exhausted, typically around age 51 in most populations, though there is wide individual variation. Research using three-dimensional imaging of whole ovaries in animal models has confirmed that as the total pool shrinks, the fraction of newly activated oocytes stays proportional to whatever remains, meaning the ovary does not compensate by activating a larger share of what is left.

Egg Quality Declines Faster Than You Might Expect

If you have heard that fertility drops sharply after 35, the mechanism behind that drop is primarily about egg quality rather than quantity alone. One of the clearest measures of quality is aneuploidy, which is when an egg ends up with the wrong number of chromosomes. A chromosomally abnormal egg, if fertilized, typically either fails to implant, miscarries, or in rare cases leads to conditions like Down syndrome. Aneuploidy affects roughly 10 to 25 percent of eggs in women in their early thirties and climbs to more than half of eggs in women over 40.¹ That is a striking shift: a woman at 32 might have three-quarters or more of her eggs chromosomally normal, while at 42 she may have fewer than half.

This matters enormously for pregnancy outcomes. A large prenatal study found that aneuploidy was about three times more common among early miscarriages than among pregnancies that continued normally.² So the reason miscarriage rates rise steeply after 35 is not mainly that the uterus is failing but that a higher proportion of embryos are chromosomally abnormal from the start.

What Goes Wrong Inside an Aging Egg

Several biological processes converge to make older eggs more error-prone. The best-studied involves proteins called cohesins, which act like molecular glue holding chromosomes together during cell division. In eggs, cohesins are loaded onto chromosomes before birth and must last for decades without being refreshed. Over time, these proteins degrade. When cohesin levels drop too low, chromosomes can separate unevenly, producing eggs with too many or too few chromosomes.³

More recent work has identified a regulatory protein called PDS5B that adds another layer to this problem. PDS5B helps with both chromosome cohesion and the assembly of the spindle, the structure that physically pulls chromosomes apart during cell division. Its levels decline with age in oocytes, and when researchers reduced PDS5B experimentally, they saw spindle defects, stalled cell division, and aneuploidy, ultimately leading to reduced fertility.⁴

The chromosome-sorting machinery is not the only thing that degrades. Older oocytes also accumulate DNA damage, and their ability to repair that damage weakens. Research has shown that aged oocytes have lower DNA repair capacity and tend to shift toward error-prone repair pathways, which can introduce mutations or structural problems.⁵ Separate work has characterized this as a weakened DNA damage response overall, leading to accumulating damage over the years an oocyte sits dormant in the ovary.⁶

Mitochondria add yet another vulnerability. Eggs contain far more mitochondria than most cells because fertilization and early embryo development are energy-intensive. As mitochondrial function deteriorates with age, the energy supply available for accurate chromosome sorting and early cell division declines, contributing to poorer outcomes.⁷ In short, aging eggs face a triple hit: weakened chromosome glue, impaired DNA repair, and flagging energy production.

Measuring Your Own Ovarian Reserve

Two clinical tests are commonly used to estimate how many eggs remain. Anti-Müllerian hormone (AMH) is a blood test that reflects the pool of small, early-stage follicles in the ovaries. Antral follicle count (AFC) is an ultrasound measurement that tallies the small follicles visible on both ovaries early in a menstrual cycle. Both decline with age and track each other fairly well: AMH correlates with the number of early antral follicles more closely than age or FSH levels do.⁸ In clinical fertility settings, both AMH and AFC show strong positive correlations with the number of eggs retrieved during IVF.⁹

One study tracking both fertile and infertile women found that AMH dropped by about 6 percent per year and AFC by about 4.5 percent per year with increasing age, and that these patterns were similar regardless of whether the women were currently fertile or seeking help for infertility.¹⁰ That consistent year-over-year decline is one reason clinicians find these markers useful for counseling even women who are not yet trying to conceive.

What a Low AMH Does Not Tell You

Here is where many people get tripped up. AMH and AFC are good at predicting how many eggs you could retrieve in an IVF cycle, but they are surprisingly poor at predicting whether you can get pregnant on your own. A study comparing women with unexplained infertility to women whose partners had male-factor infertility found that low AMH (below 0.7 ng/mL) appeared at similar rates in both groups, and the adjusted odds of having unexplained infertility were not significantly different for women with low ovarian reserve markers.¹¹

The practical takeaway: a low AMH result does not mean you cannot conceive naturally. It means you have fewer eggs remaining than average for your age, and if you needed IVF, fewer eggs would likely be retrieved per cycle. But you only need one good egg to get pregnant, and quantity does not dictate whether that one egg will be chromosomally normal. Age itself remains the better predictor of egg quality. A 30-year-old with a low AMH still has a much higher proportion of chromosomally normal eggs than a 42-year-old with an average AMH.

How Age Affects Egg Freezing Success

The distinction between quantity and quality becomes very concrete when you look at egg freezing outcomes. Modeling from a large dataset estimated that a 34-year-old with 20 mature frozen eggs would have about a 90 percent chance of at least one live birth, while a 37-year-old with the same 20 eggs would have about a 75 percent chance, and a 42-year-old roughly 37 percent.¹² To reach that 75 percent threshold, a 34-year-old would need about 10 eggs, a 37-year-old about 20, and a 42-year-old about 61. The 42-year-old needs six times as many eggs as the 34-year-old for the same odds, and retrieving 61 eggs at 42 would typically require multiple stimulation cycles.

Real-world data from a large multicenter study found that for women who froze eggs at 35 or younger, the cumulative live birth rate reached as high as 94 percent with 24 stored eggs, but dropped to about 43 percent with only 10. For women who froze at older ages, outcomes were considerably lower, with success rates of roughly 6 percent for 5 eggs and 17 percent for 8.¹³ A recent analysis of outcomes from thawed oocyte cycles found the cumulative live birth rate per started warm cycle was about 49 percent for women under 35, around 37 percent for those 35 to 40, and roughly 17 percent for women over 40.¹⁴

These numbers reinforce the point that timing matters more than total egg count. Freezing 15 eggs at 33 gives you better odds than freezing 25 at 41, because each younger egg is more likely to be chromosomally normal and capable of producing a viable embryo.

The Uterus Ages Differently Than the Eggs

A common worry is that the uterus itself loses the ability to carry a pregnancy as women get older. The evidence suggests otherwise. When researchers looked at outcomes for chromosomally normal (euploid) embryos transferred to women of different ages, the live birth rates were essentially the same whether the embryo came from the woman’s own eggs or from a younger donor’s eggs. In one cohort, the live birth rate for euploid embryos was about 40 percent in both groups, with no statistically significant difference.¹⁵

This finding is reassuring for women considering donor eggs or using embryos frozen at a younger age. It suggests that the dramatic decline in IVF success with age is driven primarily by aneuploidy in the eggs, not by changes in the uterine lining. A healthy uterus at 43 can carry a pregnancy from a chromosomally normal embryo about as well as a uterus at 33 can. There are, of course, other pregnancy complications that increase with maternal age, including gestational diabetes and preeclampsia, but the ability to implant and sustain a normal embryo appears to hold up longer than egg quality does.

Preimplantation Genetic Testing and Its Limits

Given that aneuploidy is the main driver of age-related fertility decline, testing embryos before transfer sounds like an obvious fix. Preimplantation genetic testing for aneuploidy (PGT-A) involves taking a small biopsy from an embryo created through IVF, screening its chromosomes, and selecting only normal embryos for transfer. For women over 37 or so, this can reduce miscarriage rates and improve the chance that a transferred embryo will implant.

But PGT-A is not a perfect solution. Mosaic embryos, which contain a mix of normal and abnormal cells, can be misclassified. An embryo labeled abnormal might actually have had enough normal cells to develop into a healthy pregnancy, and some abnormalities affecting only small segments of a chromosome can be missed entirely.¹⁶ For younger women with mostly normal embryos, PGT-A adds cost without necessarily improving outcomes, since their embryos already have high odds of being chromosomally normal. The test is most useful when the prior probability of aneuploidy is high, which is to say, for women in their late thirties and forties.

Smoking and Other Threats to Ovarian Reserve

Age is the dominant factor in ovarian reserve decline, but lifestyle can accelerate the timeline. Smoking is the most studied environmental exposure. Current smokers had AMH values roughly 44 percent lower than women with no active or passive smoke exposure in a study of women aged 38 to 50, suggesting a direct toxic effect on the growing follicle pool.¹⁷ Former smokers did not show the same reduction, which hints that the damage may partly reverse after quitting, at least in terms of the actively maturing follicles.

In fertility treatment settings, the impact of smoking is hard to miss. One study found that smokers required significantly more medication for ovarian stimulation and retrieved about half as many eggs on average compared to non-smokers. Cycle cancellation rates and total fertilization failure were both roughly doubled in the smoking group.¹⁸ A larger study among women seeking fertility care found that the odds of diminished ovarian reserve increased with every additional cigarette smoked per day, with the strongest effects in heavy or long-term smokers.¹⁹

Beyond smoking, chemotherapy and pelvic radiation are well-established threats to ovarian reserve, and certain autoimmune conditions and ovarian surgeries can accelerate egg loss. Less is known about subtler environmental exposures like endocrine-disrupting chemicals, though this is an active area of research. The general principle is that anything that damages or destroys ovarian tissue can push the timeline of egg depletion forward.

Why Reproductive Aging Happens So Early

From an evolutionary perspective, it is puzzling that human fertility declines decades before the rest of the body does. Most organs continue functioning well into the sixties and beyond, but the ovaries are effectively spent by the early fifties. Two main evolutionary hypotheses have been proposed to explain this. One is simply that humans only recently started living long enough for the gap to matter, meaning menopause was not “designed” by evolution but is just an artifact of longer lifespans. The other, often called the grandmother hypothesis, suggests that women who stopped reproducing earlier and redirected their energy toward helping their existing children and grandchildren survive may have passed on more of their genes than women who kept having babies into old age.²⁰

Neither explanation fully accounts for the pattern, and the debate continues. What is clear is that the fixed, non-renewable nature of the egg supply is not a flaw in the system so much as a fundamental feature of how mammalian ovaries work. Unlike sperm, which are produced continuously from stem cells, eggs are generated once during fetal development and then must last. That design works well for a reproductive window of 15 to 20 years. It just was not built with 40-year fertility in mind.

Individual Variation and What the Averages Miss

All of the numbers above are population averages, and individual women can fall far from the mean in either direction. Some women experience premature ovarian insufficiency, where the egg supply is depleted in their twenties or thirties. Others maintain robust ovarian reserves well into their early forties. Genetics plays a large role in determining where on the spectrum you fall, and family history, particularly when your mother or older sisters went through menopause, can offer a rough guide.

Conditions like polycystic ovary syndrome (PCOS) complicate the picture further. Women with PCOS often have unusually high AMH levels and antral follicle counts, which might look like a large ovarian reserve on paper but does not straightforwardly translate into better fertility, because the follicles may not mature and ovulate normally. On the other end, women who have had ovarian surgery, such as removal of an endometrioma, can see a sudden drop in their reserve from the lost tissue.

The best way to think about the age-based estimates is as a central tendency: most women follow a broadly similar curve, but your position on that curve depends on genetics, medical history, and environmental exposures. If you want to know where you stand personally, AMH and AFC testing can give you a snapshot of your current reserve, keeping in mind that these numbers speak to quantity, not quality, and that age remains the single strongest predictor of whether a given egg can produce a healthy pregnancy.