“Ovarian reserve” is a term that relates to both the quality and the quantity of your ovarian eggs – and both are important when it comes to getting pregnant. It doesn’t matter whether you’re trying to conceive naturally or via fertility treatment: if you have low-quality eggs, or not many of them, or a combination of the two, things become jolly difficult.
Age is the biggest determinant of ovarian reserve: the older you are, the lower it’ll be. If you’ve just started secondary school and you’re reading this article for some reason, now might be the time to start scouring the playground for potential sperm donors/fathers. Just kidding. I was totally kidding. I really need to stop making jokes like this.
Anyway! Here are some questions you might have about eggs – and my attempts to answer them in a way that’s easy to understand without resorting to horrendous jokes.
How many eggs do I start with? And how quickly do I lose them?
You’re born with all the eggs you’ll ever have, and there are an awful lot of them: approximately two million. But it’s not the case that you’ll lose one egg a month from puberty onwards and still have a repository of just under two million left over when you’re 84.
In fact, you’re pretty much constantly losing eggs – even when you’re still a child. By the time you hit puberty, you’re already down to your final 350,000 or so eggs – and then every month after puberty you’ll continue to lose about 1,000 eggs.
What happens to all the eggs? Well… during the average cycle, FSH is released to stimulate the growth of a small number of egg-containing follicles in the ovaries. Only one of the egg-containing follicles will grow to be big and strong enough for fertilisation – and therefore only one egg will be released into the fallopian tube. All the others will die off.
So how do we get to the “1,000” number? Well, in addition to those few “stimulated” follicles that die each month, you also lose almost 1,000 other eggs. Every single cycle.
If I’m consistently losing 1,000 eggs a month, what changes at the age of 35 to cause all the “ooh you’re too old now” scare-mongering?
At the age of 35, surely you’re just 12,000ish eggs down from where you were at the age of 34, right? Wrong: the rate of egg depletion increases as you age. By the time you’re 30, you’ll have about 12% of your eggs left. When you get to 40, you’ll be down to your final 3%. A few years later and they’ll mostly all be gone. (Menopause is typically between the ages of 48 and 55.)
You won’t suddenly start dropping a load more eggs as soon as you’ve made a wish over the 35 candles squished onto your birthday cake, but doctors tend to use that age as a shortcut to determining your likelihood of conceiving both naturally and with fertility treatment. Some clinics and hospitals will use the age of 37 or 40 instead.
(Of course, women don’t all begin life with the exact same number of eggs. And the rate at which they lose them differs slightly too: it’s all down to the natural inclinations of the body, and it’s why women go through menopause at slightly different ages.)
I started my periods really young; will that affect the age at which I lose all my eggs?
No. As we’ve seen, women lose THOUSANDS of eggs all the time – even before they hit puberty. An extra few eggs that die as a result of two extra years of menstruation means nothing in the grand scheme of things.
The same explanation goes for women who’ve spent many years on the pill: they’ll have lost thousands of eggs a month anyway, so a few hundred “saved” eggs (through not ovulating) means nothing really.
Is there anything I can do to slow down egg loss?
The number of eggs you’re born with and the rate at which you lose them is pretty much set in stone: lifestyle factors don’t really get a look-in.
Except for just ONE lifestyle factor, that is: smoking. Practically all scientific studies show that smoking accelerates the loss and quality of eggs – and as a result, it may also bring forward your menopause by several years too.
Two other factors to be aware of are radiation therapy and chemotherapy: both have been shown to reduce the quantity of eggs.
Can I find out how many eggs I have remaining?
Not directly. But a few different tests will give a good indication of whether you have “a lot” or “not a lot” of eggs left.
Find out more about them here:
- Measuring FSH levels
- Measuring AMH levels
- Measuring oestradiol levels
- Scanning for antral follicle count
What’s the deal for younger people who have a low supply of eggs?
Some younger people also – for various reasons – have a supply problem when it comes to their eggs. But they’re likely to have good-quality eggs, which means (as we’ll see) that they have a far better chance of conceiving.
Reasons you might have a low supply of eggs, even though you’re young:
- Premature menopause
- Premature ovarian failure
- Congenital adrenal hyperplasia (this is very rare)
- Pituitary tumour (this is very rare)
And, of course: smoking, radiation therapy and chemotherapy.
Fertility doctors will help you figure out the cause if you don’t know what it is already.
Keep reading… there's more below.
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Even if I’m over the age of 35, I’ll still have a few thousand eggs in there – so what’s the big deal? I only want one or two kids, after all…
Firstly, having a lower quantity of eggs makes it less likely that you’ll get pregnant: there are far fewer eggs available, so there’s less chance that one will end up getting fertilised.
But more importantly, if you’re over the age of 35, you don’t just have a smaller collection of eggs to work with. Successful implantation and fertilisation requires high-quality eggs, but the majority of your eggs are going to be of the “low quality” variety. (Think of them as hanging around in a humid environment, slowly stagnating. Or maybe don’t.) So you have a double whammy of a problem: there are fewer eggs to be fertilised, and many of those eggs are more likely to be a bit rubbish.
If you’re trying to get pregnant naturally, you’ll struggle. If you’re trying to get pregnant via IVF treatment, it’ll be a harder task than it is for younger people. Why? Two reasons:
- With a “normal” menstrual cycle, one “mature” egg gets released into the fallopian tube each month, ready for fertilisation. With IVF, the aim is for you to grow as many mature eggs as possible so that those eggs can be collected by doctors and fertilised in a lab.
(More eggs = more opportunities for at least one to fertilise.)
If you don’t have many eggs in the first place, your body will find it tougher to produce a large number of them in one go – even with the help of fertility meds.
- The eggs you do manage to produce are less likely to be good quality.
That’s why fertility clinics often won’t treat older women who are trying to get pregnant using their own eggs. This chart (from advancedfertility.com) helps to explain things:
Basically: older women tend to have fewer eggs retrieved, and even when eggs are retrieved, the live birth rate is much lower than for younger women (a result of poorer egg quality).
Tell me more about “egg quality”. What exactly does it mean?
An egg is either “good quality” or “bad quality” – there’s no “so-so quality” or “I-guess-it’ll-do quality”.
A bad-quality egg:
- Won’t fertilise, OR
- Won’t implant if it does fertilise, OR
- Has a higher likelihood of being miscarried if it does implant, OR
- Has a higher likelihood of having a genetic disorder such as Down Syndrome if it does survive to term
If you’ve ever wondered why we see more cases of infertility, miscarriage and genetic disorders in older women, that’s your reason: bad-quality eggs leads to those particular outcomes.
If you want to know the science behind it, there are two main causes of a bad-quality egg:
- Lack of energy (seriously!). Each of your eggs contains mitochondria, which can be thought of as teeny tiny batteries. When an egg is fertilised, it’s the mitochondria that give it the energy it needs to constantly divide and eventually become a foetus.
As you age, these mitochondria produce less and less energy. The result? Even if you have a successfully fertilised egg on your hands, it may simply run out of steam before it’s able to divide.
- The “wrong” number of chromosomes. An egg needs to have the correct number of chromosomes in order to develop into a healthy, genetic disorder-free baby. As you age, more and more of your eggs will contain the “wrong” number of chromosomes.
A good-quality egg doesn’t come with these problems – and about 80–90% of a 20-year-old woman’s eggs are good quality. As we age, our eggs also age – and by the time a woman is 44 years old, only about 20% are good quality. (And remember: that’s 20% of a much smaller number of eggs.)
Is it possible to determine the quality of my eggs?
It’s kind of possible to guesstimate the quality of your eggs by looking at a few factors:
- Your age. Nearly all women under 35 will have good-quality eggs.
- The number of eggs you have left – as indirectly determined by blood tests for FSH, AMH and oestradiol levels, as well as an antral follicle count. This usually comes down to age again: if you don’t have many eggs left, it’s probably due to how old you are – and that affects the quality of your eggs too. If you’re young and a smoker, you’ll also have a reduced egg count compared to the norm, and the quality of those eggs will be worse.
- The outcome of any recent pregnancies. If it takes you a long time to conceive or you’ve suffered early miscarriages, it could mean decreasing egg quality.
- The outcome of any recent IVF attempts. If none/very few of your eggs were successfully fertilised – or if you constantly had problems getting fertilised eggs to implant – it might indicate a problem with egg quality.
- The results from pre-implantation genetic screening (PGS). The screening identifies chromosomal abnormalities in embryos, so you’ll need to already be having fertility treatment like IVF to participate.
A high number of abnormalities in your embryos is an accurate predictor of the quality of your eggs in general. (Over 90% of chromosomal abnormalities are thought to come from the egg rather than the sperm.)
(Note that the HFEA currently doesn't recommend PGS, because there's little evidence so far that it improves people's chances of pregnancy.)
Does anything other than age affect egg quality?
Yup. In fact, younger people can have poor-quality eggs too – and it’ll also affect their success rates with getting pregnant naturally or via fertility treatment. (Having said that, it won’t affect their success rates to the same extent as older people, because they’re more likely to have more good eggs somewhere among their abundant collection).
In addition to age, egg quality is affected by the following:
- Drug use
- Ovarian cysts
- Some immunological disorders
- Radiation therapy and chemotherapy
Age is the most important determinant – so you’re unlikely to improve the quality of your eggs through lifestyle changes if you’re totally over the hill (which in this context is your mid-40s onwards).
But if you’re in your 20s to early 40s, you can improve the quality of your eggs by losing weight if your BMI is over 30, and by quitting smoking and drug use.
Remember: if you’ve been struggling to conceive and you make these lifestyle changes, you might not actually need fertility treatment at all. And if you do need fertility treatment, it’s more likely to be successful.
Is there anything else I can do to improve egg quality? Incense? Crystals? Chanting? Anything?
If you google the question, there’s PLENTY you can do – but most are pure hogwash. (Seriously: going gluten-free won’t do anything other than diminish your mermaid-themed-nursery fund and make you crave real bread.)
But there are a few suggestions that fertility specialists either support or believe won’t have any adverse effects – so there’s no harm in trying them. They are:
- Get your hormones more balanced by de-stressing, sleeping well, and regulating your blood sugar.
- Give your mitochondria more energy by taking CoQ10 as well as vitamins A and E.
- Neutralise free radicals in your body (which speed up the aging process of your eggs) with a diet rich in antioxidants, e.g. brightly coloured fruit and veg, green tea and – in moderation – red wine.
- Have acupuncture to increase blood flow to the ovaries. A good blood flow enables more nutrients to reach the eggs and improve their overall health.
- Start taking a B vitamin called Inositol, which is thought to improve egg quality by increasing insulin sensitivity of the ovaries.
- Talk to your doctor about a hormone called DHEA (dehydroepiandrosterone): recent studies indicate that it may improve egg quality, but it’s a pretty potent hormone and needs to be taken under supervision.
If I have (or probably have) poor-quality eggs, will IVF help?
That depends. If the poor quality is down to advanced age, there’s a chance you’ll be refused fertility treatment because you also have very few eggs to work with.
This chart from the Human Fertilisation & Embryology Authority (HFEA) shows just how much age affects your chances of successful IVF:
If you’re still young and struggling to get pregnant as a result of poor-quality eggs, there’s a good chance IVF will help. There are a couple of reasons why:
- With IVF, the aim is for you to grow as many mature eggs as possible, so that those eggs can be collected by doctors and fertilised in a lab. More eggs = a higher chance that at least one of them will be of the high-quality variety.
- Your embryos can undergo preimplantation genetic screening (PGS) to check for abnormalities – which increases your likelihood of a successful pregnancy because only a healthy embryo will be put back in.
There’s a lot of information here. If you could summarise everything for me, that’d be great…
- Egg quantity AND egg quality are important when it comes to fertility.
- You can’t do anything about the number of eggs you have left (other than give up smoking).
- But you can take steps to improve your egg quality – and doing so will actually make it easier to conceive naturally – meaning you may no longer need fertility treatment.
- But age trumps everything: if you’re over the age of 35 (and particularly if you’re over the age of 40), you’ll struggle to improve your egg quality in a way that overrides the loss in quality caused by age.
- If you’re relatively young and you have either poor-quality eggs or not many of them, you have a better chance of conceiving (either naturally or through fertility treatment) compared to older women.