A woman loses roughly 1,000 immature eggs every month once her menstrual cycles begin. Only one of those eggs (occasionally two) actually gets released during ovulation. The rest break down and are reabsorbed by the body in a natural process called atresia.
Why You Lose So Many More Than One
Each month, a group of immature eggs begins developing inside small fluid-filled sacs called follicles. Hormonal signals push this batch forward, but only the single strongest follicle matures fully and releases its egg at ovulation. The remaining follicles in that batch, sometimes dozens of them, stop developing and die off through programmed cell death. This isn’t a malfunction. It’s the body’s built-in quality control system, selecting the most viable egg while discarding the rest.
The roughly 1,000 eggs lost per cycle includes both the follicles that started developing and never made it, and a larger number of dormant eggs that degrade without ever entering the maturation process at all. Less than 0.01% of all eggs a woman carries will ever reach ovulation. Out of the 1 to 2 million eggs present at birth, only about 400 will ovulate across an entire lifetime. The other 99.9% disappear through atresia.
How Your Egg Count Changes With Age
The decline starts before you’re even born. A female fetus has her peak egg count at around 20 weeks of gestation, typically 6 to 7 million. By birth, that number has already dropped to 1 to 2 million. By puberty, roughly 300,000 to 500,000 remain. By age 30, the count is down to about 70,000 to 100,000. By menopause, which typically occurs around age 50 or 51, fewer than 1,000 eggs remain and natural fertility ends.
The rate of loss isn’t constant. It accelerates noticeably after age 35. While the monthly loss of around 1,000 eggs is a useful average for reproductive years, that number climbs in your late 30s and 40s as the remaining pool shrinks. This acceleration is one reason fertility specialists flag 35 as a turning point, not because fertility disappears overnight, but because the pace of depletion picks up.
Can Birth Control Slow the Loss?
This is one of the most common misconceptions about the pill. Since hormonal contraceptives suppress ovulation, it seems logical that they’d “save” eggs and delay the decline. They don’t. The vast majority of monthly egg loss comes from atresia, not ovulation. Stopping ovulation prevents the release of one egg per cycle, but the other 999 or so still break down on schedule. Birth control does not preserve your ovarian reserve or push back menopause.
What hormonal contraceptives do affect is how your reserve appears on tests. Women using the combined pill, vaginal ring, or implant show AMH levels (a hormone used to estimate remaining eggs) that are 20 to 25% lower than women not on contraception. This doesn’t mean their actual egg supply is lower. After stopping the pill, AMH levels bounce back by about 53% and follicle counts rise by about 41%, returning to normal within two months. If you’re planning fertility testing, your doctor will likely want you off hormonal contraception for at least two months before drawing labs.
Factors That Speed Up Egg Loss
Smoking is the most well-documented lifestyle factor that accelerates egg depletion. Women who smoke have measurably lower ovarian reserve markers and tend to reach menopause earlier than nonsmokers. In fertility treatment settings, smokers produce fewer mature eggs during stimulation cycles (about 8 to 9 compared with 12 for nonsmokers) and have significantly lower pregnancy rates. The mechanism appears to be a direct increase in follicle death at the pre-antral stage, meaning smoking doesn’t just damage egg quality but actively speeds up the rate at which eggs are lost each month.
Other environmental exposures linked to faster depletion include phthalates (found in many plastics and personal care products), bisphenol A, and certain pesticides. These substances appear to increase the rate of follicle breakdown, potentially leading to earlier menopause onset.
How Doctors Measure Your Remaining Eggs
Two tests give the clearest picture of ovarian reserve. The first is a blood test measuring AMH, a hormone produced by developing follicles. Higher levels suggest a larger remaining pool. AMH stays relatively stable throughout your menstrual cycle, so it can be drawn on any day. The second is an antral follicle count, an ultrasound performed early in the cycle that counts the small, visible follicles in both ovaries.
Both tests estimate how many eggs you have left, but neither predicts egg quality, which matters just as much for fertility. A 25-year-old with a lower-than-average egg count still typically has better egg quality than a 40-year-old with an average count. In studies comparing the two tests, antral follicle count was slightly better at predicting low ovarian response, while both performed similarly for predicting high response.
Does Egg Freezing Use Up Your Reserve Faster?
No. During egg freezing or IVF, fertility medications stimulate multiple follicles to mature in a single cycle instead of just one. This can feel counterintuitive, since 10 to 15 eggs might be retrieved at once. But those eggs come from the batch of follicles that were already recruited for that cycle and would have died off through atresia anyway. The medications rescue follicles that were destined to be lost, rather than pulling from future months’ supply. No current evidence suggests that egg freezing or IVF stimulation reduces your overall reserve or affects your ability to conceive naturally afterward.