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Home/Cycle Matters / Reproductive Health

5 Female egg cell facts: How many eggs does a woman have?

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Written by Lauren McKay

Lauren McKay

Lauren McKay is a writer and journalist with more than ten years of experience writing across a variety of topics. She is a passionate advocate for driving women’s health knowledge and is a trained yoga teacher. She earned a Masters in Creative Writing from the University of Glasgow and currently lives in Scotland.
Jack in a suit and tie holding a microphone and giving a presentation.

Fact checked by Jack Pearson, Medical Affairs Manager at Natural Cycles

Jack Pearson

Dr. Jack Pearson is a previously HCPC registered Embryologist with a PhD in reproductive medicine. Prior to joining Natural Cycles leading Medical Affairs, he worked for more than 10 years in a clinical setting working at some of the busiest fertility clinics in the UK. Today he spends most of his time working with experts at the world’s leading institutions to carry out important research with the vision to further the field of female health. He earned his PhD from the University of Sheffield specializing in Sperm Metabolism and currently lives in London.

Key takeaways:

  • Females have six to seven million eggs when they’re a fetus at 20 weeks gestation.
  • Females are born with between one and two million eggs. 
  • The number decreases until a person stops ovulating and reaches menopause, at which point fewer than 1,000 remain.
Get ready to learn some surprising facts about the female egg cell! In this article, we’ll dive deep inside the workings of the menstrual cycle and explore the small and fragile cell that’s crucially important when it comes to fertility. Read on to find out why human eggs are so special and how the life of the egg cell is closely tied to planning or preventing pregnancy.

This article is also available in Spanish.

1. An egg cell is usually released every cycle

Most women release an egg cell every cycle – this is called ovulation. It is possible to miss ovulation (known as anovulation), meaning that an egg isn’t released that cycle.

How are eggs released?

Eggs are released through the process of ovulation, which is regulated by hormones. During the menstrual cycle, rising estrogen levels trigger a surge in luteinizing hormone (LH), causing the mature follicle in the ovary to rupture and release the egg. The released egg then travels down the fallopian tube, where it may be fertilized by sperm. 

Hormonal birth control works by suppressing ovulation. This is how pregnancy is prevented: by removing the egg cell from the equation altogether. When ovulation doesn’t happen in a regular menstrual cycle, this is called an anovulatory cycle. Anovulatory cycles are common, and most women are likely to experience them at some point in their lives. You may not realize you haven’t ovulated if you aren’t tracking your menstrual cycle.

How many eggs are released during ovulation?

You have a huge number of eggs in your reserve, but they won’t all be released. That’s because every month, your body selects a group of eggs as a candidate for ovulation – but usually, only one egg is released, becoming the single egg that’s released that cycle.

So, in the majority of cases, only one egg is released during ovulation – but there are exceptions. Some women can release two egg cells per cycle (within 24 hours of each other), which can result in the conception of fraternal twins. Identical twins are made when the fertilized egg cell divides in two. Identical twins grow in the same amniotic sack and, unlike fraternal twins, are genetically the same.

During the course of your lifetime, you’ll only release about 500 eggs. The rest of the eggs that are chosen as contenders for ovulation but don’t end up being released undergo a process called atresia, which means that the eggs are reabsorbed back into the body – or, in other words, they die off. This is a completely normal process and nothing to be worried about.

2. You are born with all your egg cells

Did you know that every woman is born with all her eggs already inside her ovaries? Because you’re born with all your eggs, this actually means that your eggs were once inside your grandmother and also your mother when you were a fetus in her womb. That means your mother carried the egg cells, which may one day be fertilized and grow into her own grandchild!

How many eggs are females born with?

According to the American College of Obstetricians and Gynaecologists (ACOG), a female fetus will typically have between 6 and 7 million eggs (technically known as oocytes) at 20 weeks of gestation. By the time of birth, that will have dropped to around 1-2 million eggs. Many of these eggs will be released throughout your lifetime – but not all of them. By the time a girl hits puberty, the number of eggs has usually reduced to 300,000–500,000, which is still more than will ever be released.

Why does menstruation not start at birth?

If women are born with all the eggs they’ll ever have in their lifetime, then why don’t they start releasing them immediately? Well, while the eggs are there, other factors also determine when eggs will be released.

Puberty begins when the hypothalamus (an area of the brain that produces hormones) secretes gonadotropin-releasing hormone (GnRH), which in turn stimulates the pituitary gland to emit two different hormones: luteinizing hormone (LH) and follicle-stimulating hormone (FSH). 

FSH stimulates the follicles on the ovaries to grow, preparing the eggs for ovulation.As these follicles grow, they cause estrogen levels to rise. It’s this rise in estrogen levels that causes a girl to get her first period, also known as menarche.

So, there’s a long process to go through until puberty begins, and it usually takes around two years from the first signs of puberty until a girl gets her first period.

How many eggs does a female have in their 20s and 30s?

By the time you hit puberty, the number of eggs you have will have decreased to around 300,000 - 500,000 – and this number continues to decline throughout your lifetime. After your first period, you lose around 1000 eggs a month. This might sound dramatic, but it’s all part of the natural process. 

When you reach your 20s, you’ll typically have around 150,000 - 300,000 eggs left in your ovarian reserve. In your early 30s, you’ll often have around 100,000 -150,000 eggs in your reserve, and by your late 30s, that number drops, with the ACOG suggesting that most women have around 25,000 eggs at 37 years old.

As the number of eggs declines, so does your fertility, with lower fertility typically occurring in your late 30s. Just because fertility rates typically decline at this age, it’s important to remember that many women do successfully get pregnant in their late 30s (and beyond) – but it’s always important to be aware of the facts if children are in your future, so you can better plan.

How many eggs remain at 40?

In your 40s, it’s estimated that you’ll have around 5,000 to 10,000 eggs in your ovarian reserves. You can still get pregnant as long as you’re ovulating, but the chances of conceiving do become lower, which means it can be harder to get pregnant. If you’re planning to have a child in your 40s, it’s a good idea to speak to your healthcare provider for advice on the best options for you.

3. The quality of human eggs gets worse over time

As we get older, so do our cells and the female egg cell is no exception. Although women are born with millions of eggs, the quality of these goes down over time. Many die off before we even hit puberty, meaning we’re left with around 300,000 - 500,000 egg cells by the time menstruation begins.

Why does egg quality decrease as you age?

It’s not just the quantity of eggs that decreases as you get older, but also the quality. This is mostly down to the age of the eggs. Because you’re born with all of the eggs you’ll ever have, those eggs have been around for quite a while by the time you hit your 20s, 30s, and 40s.

Your eggs start to divide every month before ovulation, in a process called meiosis. As you get older, there’s a greater chance of errors happening during this process, which can lead to chromosomal abnormalities in the eggs. 

Chromosomal abnormalities in eggs can result in reduced fertility, an increased risk of miscarriage, and a higher likelihood of genetic disorders in offspring if fertilization occurs. This is one of the reasons why fertility declines with age and why there's an increased risk of pregnancy complications in older individuals.

Menopause

Each month a woman continues to lose egg cells – and at 51 years old (which is the average age of menopause in the United States), the ACOG reports that women will have around 1,000 eggs left.

Everyone’s different and will go through menopause at a different age depending on how many eggs you’re born with, and how quickly you lose those eggs. As the supply of eggs decreases and ovulation becomes more irregular, your body also starts to produce less estrogen and progesterone, causing symptoms of menopause.

While we're busting myths, it’s important to know that taking hormonal birth control or being pregnant cannot preserve egg cells or delay menopause. Our reserve of egg cells continues to deteriorate over time, regardless.

4. The female egg cell is bigger than you think

Most cells aren’t visible to the naked eye; you need a microscope to see them. The human egg cell is an exception – it’s actually the biggest cell in the body and can be seen without a microscope. That’s pretty impressive.

Compared to the other human cells, egg cells are huge. They are 100 microns in diameter (that’s a millionth of a meter) and are about as wide as a strand of hair. That may sound small, but no other cell comes close to being that large.

5. The female egg cell has a short life after ovulation

Once ovulation has happened, the female egg cell that’s released starts to deteriorate very quickly, and the fertile window starts to close. After 12-24 hours, the egg cell will die, and it won’t be possible to become pregnant again until the next cycle. 

For this reason, the best time to conceive is actually the day before ovulation. Compared to egg cells, once released, sperm are more resilient and can survive in the female reproductive tract for up to five days! Sperm survival is dependent on the right conditions, such as the consistency of cervical mucus. Identifying ovulation is a key step in planning a pregnancy.

Fertility options

There’s no denying that the quantity and quality of our eggs decline as we get older. That doesn’t necessarily mean you’ll find it hard to get pregnant – plenty of people of all ages successfully conceive and give birth every year! But if you are having trouble conceiving, there are some options you might want to consider to increase your chances of getting pregnant.

Egg donation

Egg donation is when a woman donates her eggs to another individual or couple who are unable to conceive with their own eggs. 

An egg donor takes medication to stimulate the egg production process, resulting in multiple eggs, while the recipient undergoes a course of hormone therapy to prepare their uterus for pregnancy. The donor eggs are fertilized in a laboratory, and then one or more embryos are placed into the recipient’s uterus. 

Success rates for egg donation largely depend on the age of the egg donor rather than the age of the recipient, according to the Human Fertilisation and Embryology Authority (HFEA). Their studies show that the birth rate per embryo transferred for patients aged 18-34 who were using their own eggs was 33%, compared to 5% for patients aged 43-50 – but birth rates were above 30% for all ages when using donor eggs.

Egg freezing or fertility preservation

If you know you want to have children at a later stage, you may consider preserving your young, healthy eggs by freezing them. This involves taking medication to stimulate your ovaries to produce multiple eggs, which are then retrieved and stored in a laboratory (at sub-zero temperatures) until you want to use them.

At that point, they’ll be thawed and then fertilized using either your partner’s sperm or sperm from a donor. Studies by HFEA show that if eggs are frozen below the age of 35, the chances of success will be higher than the natural conception rate as the woman ages.

Assisted reproductive technologies

You may also consider assisted reproductive technologies like in vitro fertilization, more commonly known as IVF. The process of IVF involves taking a female egg cell and fertilizing it with a male sperm cell in the laboratory – and one cycle can take between three and six weeks.

Everyone is different, and every IVF clinic is different, but as a rough guide, here are the success rates according to HFEA:

  • 32% for women under 35
  • 25% for women aged 35-37
  • 19% for women aged 38-39
  • 11% for women aged 40-42
  • 5% for women aged 43-44
  • 4% for women over 44

IVF isn’t the only assisted reproductive technology. Others include:

  • Donor insemination, when the sperm from a donor is put directly into the vagina of the person who wants to get pregnant
  • IUI (Intrauterine insemination), when the sperm from a donor or partner is put into the womb of the person wanting to get pregnant
  • Surrogacy, when another woman carries a baby for someone else – and the eggs can come from either party

The fertility journey is entirely personal, and what works for one person might not work for another.So, it’s important to understand the different fertility options available to work out which one is right for you.

Birth control and the menstrual cycle

Just as knowing when you’re fertile can help plan a pregnancy, this science can also be used to prevent pregnancy. Once you have identified the fertile window, there are only six days in the menstrual cycle when it’s possible to become pregnant. Abstaining from sex or using a condom on days when there is a risk of pregnancy is a natural method of birth control.

The tricky part comes in when you consider the fertile window opens before ovulation even happens, so by the time you’ve ovulated, it’s too late to prevent pregnancy. This is where Natural Cycles comes in. By taking your temperature regularly and inputting it into the app, it’s possible to learn your unique cycle and find ovulation through a rise in body temperature. 

Unlike traditional fertility awareness-based methods, Natural Cycles is powered by an algorithm that can learn the pattern of your unique cycle and predict ovulation. This means that the birth control method is precise and tailored to you. And unlike the calendar method, it does not predict your fertility based on the average menstrual cycle.

Ready for non-hormonal birth control? Find out if Natural Cycles is right for you!

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