Female Fertility: The Number of Eggs at Birth

Here’s a surprising truth: babies with ovaries are actually born with all the eggs they will ever have. Kind of unfair, isn’t it? While men can make new sperm daily, women eggs are set from day one. This fact is central to the ovulation cycle fertility process and explains why fertility shifts so much with age.

And here’s something worth and MUST noting: fertility challenges aren’t just a “personal” issue. They show up in national numbers, too. For example, Malaysia’s female fertility rate has dropped steeply, reaching a record low of 1.55 births per woman in 2023. That’s a big change, right?

Are babies with ovaries born with eggs?

Yes. Babies with ovaries already carry all the eggs they will ever have. These eggs, called oocytes, rest inside tiny sacs called follicles in the ovaries. They stay there quietly until puberty.

For years, scientists believed no new eggs were made. But in 2004 (yes, more than 10 years ago), one study on mice claimed that ovaries might create new eggs. It caused a stir, but follow-up research didn’t support the idea. Today, most experts agree: humans are born with a fixed supply. So no, there’s no refill button for women's eggs.

How many women eggs at birth?

During early fetal development, a baby with ovaries can have up to 6 million eggs. By birth, that number already drops to 1–2 million. By puberty, only 300,000–400,000 remain.

That’s a massive decline before ovulation cycle fertility even begins. It’s like starting a race with a million runners, but only a fraction ever make it to the finish line.

Why doesn’t the ovulation cycle start at birth?

If women eggs are present from day one, why doesn’t the cycle start right away? The answer is hormones. The ovulation cycle fertility process doesn’t switch on until puberty.

When puberty begins, the hypothalamus in the brain produces GnRH (gonadotropin-releasing hormone). This triggers the pituitary gland to release follicle-stimulating hormone (FSH), which gets follicles ready to grow eggs.

Menstruation typically starts around age 12, about two years after breast development begins. For some, it starts as early as 8; for others, as late as 15. 

How many eggs are lost each month?

Each month, the body picks a group of eggs. Only one usually becomes the dominant follicle and gets released during ovulation. The rest die off in a process called atresia.

So, how many women eggs are released during ovulation? Just one per cycle, most of the time. Sometimes two, which can lead to fraternal twins.

At the same time, around 1,000 immature eggs die monthly. Scientists still don’t know why, but it happens no matter what.

How many eggs by age?

• Puberty: Around 300,000 to 400,000 eggs.
• 30s: Fertility starts dropping, more quickly after 35.
• 40s: Less than 10% of eggs remain, and chances of pregnancy are under 5% per cycle.
• Menopause (average age 51): Fewer than 100 eggs left.

By age 37, research shows most people have about 25,000 eggs left. From there, menopause is usually about 15 years away.

Why does egg quality decrease with age?

Quantity matters, but so does quality. As women age, their eggs are more likely to develop chromosomal issues. This happens during the final cell divisions eggs go through before ovulation.

According to the American College of Obstetricians and Gynecologists (ACOG), older eggs are more likely to create embryos with abnormalities. That explains why miscarriage rates rise and why the chances of conditions like Down syndrome increase with age. In other words: more birthdays mean fewer “perfect” women eggs.

While hormones, pregnancies, or supplements don’t change these facts, folic acid is often recommended before and during pregnancy. It helps lower the risk of chromosomal problems like neural tube defects, even if it can’t increase egg count.

Factors that speed up egg loss

Most of the decline in egg count is natural and can’t be stopped. But a few factors can speed things up:

1. Smoking

A study found that smoking not only speeds up egg loss but also lowers egg quality. Researchers believe toxins in tobacco directly damage the ovaries. Quitting won’t restore lost eggs, but it can slow further decline. So yes, smoking really is that bad for fertility.

2. Cancer treatments

Some chemotherapy drugs and radiation therapies can cause a significant drop in egg count. In some cases, they may even lead to permanent infertility. Doctors sometimes recommend freezing eggs before treatment to help preserve future fertility.

3. Ovarian failure or early menopause

In rare cases, ovaries stop working earlier than expected, sometimes in the 30s. This condition, called premature ovarian insufficiency, causes eggs to be lost faster than usual and can lead to early menopause. It’s uncommon, but for those affected, it can be a shocking change of plans.

What happens at menopause?

Menopause begins when the ovulation cycle fertility process runs out of eggs. Once the ovaries can’t release the women eggs, they also stop making enough estrogen, and periods end.

The average age of menopause in Malaysia is 45 and 55. But it can happen earlier or later. Others may lose eggs faster and face fertility struggles or early menopause.

The Bottom Line

Babies with ovaries are born with all the women eggs they’ll ever have. From 6 million in the womb, to 1–2 million at birth, to fewer than 100 at menopause, the decline is steady and natural.

Knowing how many eggs are released during ovulation, how fertility changes with age, and what speeds up egg loss can help people make informed choices. It may sound harsh, but biology doesn’t bend and planning ahead is the smartest move.