How many eggs does a woman have and need?

Understanding how many eggs you have and what lifestyle factors impact your ovarian reserve can help you make more informed decisions about your chances of conceiving. 

Unlike men, who  continually produce sperm for their entire life, women are born with all the eggs they’ll ever have. Around two million, to be precise. So, a woman's ovarian reserve is established before birth. As you age, your ovarian reserve gradually declines, as does your fertility.

Understanding ovarian reserve

Ovarian reserve and egg quantity

Ovarian reserve is the number and quality of eggs in a woman's ovaries. “Diminished ovarian reserve”, on the other hand, is when you have fewer eggs compared to women your age.

Ovarian reserve can play a critical role in your chances of conceiving, especially if you’re undergoing in vitro fertilisation (IVF). Luckily, the number of eggs a person has isn’t the only factor that affects the ability to get pregnant. 

How many eggs are women born with?

So, how many eggs does a woman have? It’s different for every woman; there’s no way to know the exact number of eggs you have at any given time, but we have a pretty good idea of how many eggs the average, healthy woman has throughout her life.

Women have the highest number of eggs while they're still in their mother's uterus. A 20-week-old female foetus has about seven million eggs — fascinating, right? However, by the time you're born, this number drops to around one to two million. 

How many eggs remain by puberty?

Once a female enters puberty and starts having menstrual cycles, that number of eggs she has drops to somewhere between 300,000 and 500,000.

The significant drop in the number of eggs from birth to puberty is normal and occurs due to a process called atresia where eggs naturally wither and get reabsorbed by the body.

The maturation of eggs takes around two weeks but can be divided into two distinct stages. In the initial stage, many eggs (up to 1000) begin to develop and start to mature. The second stage requires gonadal hormone stimulation to promote further maturation. As pre-pubescent females do not produce the necessary hormones, all the eggs that have begun to mature degenerate.

How many eggs are lost per period?

Even though only one egg is typically released during ovulation, your ovaries actually prepare many eggs every month. Usually during each menstrual cycle, one egg becomes dominant and continues to mature. The remaining eggs that aren't released will be re-absorbed into the body. This is why women lose so many eggs each month.

How many eggs does a woman need to get pregnant?

A woman only needs one egg to get pregnant. Each month during ovulation, typically one egg is released from her ovaries, even though more than one is often produced. If that egg is fertilised by sperm, it can result in pregnancy. However, the likelihood of conception depends on many factors, including the timing of intercourse, sperm and egg quality, and the overall reproductive environment. So, while only one egg is needed, fertility and pregnancy involve a complex interplay of factors that go beyond just the number of eggs available.

Do contraceptives affect ovarian reserve?

You may have heard that taking hormonal contraception, like the combined pill, can harm your chances of getting pregnant later. However, this isn’t true. These contraceptives prevent pregnancy by stopping ovulation and making it difficult for sperm to reach the egg. But, they don’t affect your ovarian reserve. That said, another misconception is that because contraception stops you from ovulating, that you’re preserving your fertility – this isn’t true either.

Age and ovarian reserve

Your ovarian reserve gradually declines as you get older, and both the quantity and quality of eggs decrease. 

With age, there's an increased risk of your eggs having chromosomal abnormalities, which means the egg is missing or has extra DNA or chromosomes. This can cause problems with implantation during pregnancy and congenital disabilities later on. It also carries an increased risk of miscarriage.

Although it may sound scary, getting pregnant at an older age doesn't mean your baby will have a genetic disorder. It's still possible to have a healthy pregnancy later in life, and your doctor can perform tests during the first and second trimesters of pregnancy to check if your baby is at risk of congenital disabilities. Your doctor will also keep a close eye on your pregnancy to make sure that you and your baby are healthy.

Why does egg quality decrease as you get older?

Egg quality decreases as a woman gets older due to the natural aging process, which affects both the eggs and the ovarian environment.

Over time, your eggs accumulate DNA damage due to environmental exposure and the gradual decline in the body's ability to repair genetic material. Additionally, mitochondrial function, which provides energy for egg development, declines with age, making it harder for eggs to mature properly or support early embryo growth.

Individual variation

Age is only one factor affecting how quickly you lose your eggs or their quality. The rate at which your ovarian reserve declines depends on your medical history, genetics, and any medical conditions. And sometimes, it’s idiopathic, meaning there’s no apparent cause. 

Lifestyle factors like smoking and excessive alcohol consumption can also impact your ovarian reserve negatively. Additionally, chemotherapy, radiation, and ovarian surgery can speed up egg loss. If you need to undergo one of these treatments, talking to your healthcare provider first is important. They can explain the potential consequences and offer options like egg or embryo freezing to help preserve your fertility (more on that below).

How many eggs are left at age 30?

By the time a woman hits her thirties, it is estimated that around 90% of the eggs she was born with will be gone. Of course, this varies between individuals but on average, around 100,000 to 150,000 eggs will be left by your early thirties.

How many eggs do you have at 35?

After the age of 30, the number of eggs you have reduces significantly. By the age of 35, the approximate number of eggs remaining is 50,000. By age 37, you have around 25,000 eggs.

How many eggs does a woman have at 40?

Your ovarian reserve continues to drop and by the age of 40, women have around 5000 eggs remaining. Once you reach menopause (which on average, occurs at the age of 51) you will still have approximately 1,000 immature eggs left in your ovaries.

What happens to your eggs at menopause?

By the time menopause is reached, your ovarian reserve has been largely exhausted. The remaining eggs are often of poor quality and unlikely to mature properly. In addition, your body stops producing the hormones necessary for ovulation, so these eggs can't be fertilised and turn into a pregnancy.

Assessing ovarian reserve

Although no test can tell you exactly how many eggs you have at any given time, some tests can help predict your ovarian reserve. These include: 

• Anti-Müllerian hormone (AMH) test. This blood test measures AMH, a hormone produced by cells inside the follicles of the ovaries that corresponds to egg count. The higher the level of AMH, the more eggs there are. 

• Follicle-stimulating hormone (FSH) and estradiol blood tests, which measure your ovarian function.

• Antral follicle count, which uses a transvaginal ultrasound scan to count the number of follicles visible in your ovaries.

Knowing your egg count is especially important if you're undergoing IVF. The more eggs you have during the ovarian stimulation and egg retrieval process, the better your chances of success. Unfortunately, doctors can only develop the available eggs, and sometimes some are lost along the way. So, a low egg count is something to keep in mind.

Preserve your fertility with egg freezing

If a woman wants to keep her fertility options open, she can consider egg freezing. This process involves collecting a woman's eggs, freezing them, and then thawing them later on to be used for fertility treatment. 

Egg freezing helps to preserve fertility by freezing the eggs at their prime quality, and using them when the woman is ready to have a baby. At what age a woman should freeze her eggs does depend on a range of factors including her personal circumstances. However, as the number of eggs you have and the quality of them declines with age, freezing them when younger can give you a higher chance of a successful pregnancy in the future.

Egg freezing can be a helpful option if:

• you have a medical condition (or are undergoing a treatment) that could impact your fertility, like cancer. There may be NHS funding options available depending on where you live.

• you're worried about your fertility decreasing, but you're not quite ready to start a family.. This is known as “elective egg freezing,” and it isn’t available on the NHS, so you’ll have to do it with a private fertility clinic. Some employers offer support for elective egg freezing.

• you're transitioning from female to male and want to preserve your fertility before starting hormone therapy or having gender reassignment surgery. 

Getting pregnant can be a complex and emotional journey, and it's easy to feel anxious about the ins and outs of conception — especially when society loves reminding women about their "biological clock". 

If you're planning on starting a family later in life or undergoing IVF, it's helpful to know how ovarian reserve may impact your chances, but remember that the number of eggs you have is just one piece of the fertility puzzle. If you're worried about your ovarian reserve or want to know more about how it can affect your chance of getting pregnant, get in touch with one of our fertility advisors.

References

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3. Mansour, D., Gemzell-Danielsson, K., Inki, P., & Jensen, J. T. (2011). Fertility after discontinuation of contraception: A comprehensive review of the literature. Contraception, 84(5), 465-477. https://doi.org/10.1016/j.contraception.2011.04.002 

4. Cimadomo, D., Fabozzi, G., Vaiarelli, A., Ubaldi, N., Ubaldi, F. M., & Rienzi, L. (2018). Impact of maternal age on oocyte and embryo competence. Frontiers in endocrinology, 9, 327. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6033961/

5. Hassold, T., & Hunt, P. (2001). To err (meiotically) is human: the genesis of human aneuploidy. Nature Reviews Genetics, 2(4), 280-291. https://www.researchgate.net/publication/12049418_To_ERR_meiotically_is_human_The_genesis_of_human_aneuploidy 

6. Van Heertum, K., & Rossi, B. (2017). Alcohol and fertility: how much is too much?. Fertility research and practice, 3(1), 1-7. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5504800/ 

7. (n.d.). Fertility problems: Assessment and treatment. National Institute for Care and Health Excellence. https://www.nice.org.uk/guidance/CG156/chapter/recommendations#prediction-of-ivf-success