It’s common knowledge that as a woman ages, her fertility drops. What is it about the age of an egg that could stop you getting pregnant?

1Image taken from dailymail.co.uk

 

By Hayley Fryer

Have you ever seen a pregnant 60-year-old? Probably not.

It’s a well-known fact that when women reach a “certain age”, they are no longer able to have children, and reach a stage in life called the menopause.

Although the menopause is the official end-point of when a woman can fall pregnant, the chance of you getting pregnant starts to decrease from a much earlier age.

The percentage of women able to easily fall pregnant begins to decline steadily from around age 35.

This reduction in fertility is well documented and easily visible in society, with many of the women seeking IVF and other methods to aid pregnancy, being of an older age.

Egg quality declines with age, which means that as you get older, the number of eggs that would result in a viable embryo decreases.

A decline in egg quality is a completely natural process which happens to all women. An issue has arisen in recent years as many couples are now postponing having children until later in life. This could mean that by the time they try to fall pregnant, they struggle to conceive.

One of the reasons why egg quality is thought to decrease is that in older eggs, chromosomes are not able to adhere well to each other. Eggs are meant to undergo cell divisions before they can become an embryo. If the chromosomes are not stuck to each other well, the division may happen too soon. This results in eggs which have the wrong number of chromosomes in them, a situation called aneuploidy.

This can result in viable embryos, for example people with Down syndrome have an extra copy of chromosome 21, but often these eggs are rendered infertile.

Although chromosomal adhesion can explain some causes for egg infertility, it cannot account for all egg infertility in older woman.

Research by Shoma Nakagawa and Greg FitzHarris may be able to shine light on another cause of egg infertility.

 

The research

Research by Nakagawa and FitzHarris may have found another reason why egg quality decreases with age.

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Some of you may have clicked on this blogpost because of the word “cleavage” in the title.

Sorry to disappoint, but I’m not talking about that type of cleavage.

As discussed previously, eggs undergo division before they can be fertilised. This process is referred to as cleavage.

Nakagawa and FitzHarris have found that in the eggs of older mice, this cleavage is often chaotic.

They believe that the cause of this chaotic cleavage is the microtubules. These are structures within the cell which organises the cell content within a dividing cell. One of their roles is to put the chromosomes at opposite ends of the cell, so that an even number is present once the cell has split into two.

In the eggs taken from older mice, the microtubules often sent the chromosomes in places they should not be, causing up to four groups of chromosomes instead of the normal two.

As a result, these eggs will have incorrect numbers of chromosomes, and therefore likely be infertile.

A possible reason why microtubules may not function as well in older woman is that they require energy to work properly. This energy is usually provided by mitochondria, but in older cells, mitochondria is less-able to produce energy.

 

Is it all the woman’s fault?

The quality of sperm decreases as a man gets older

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There’s a common misconception that men have the same level of fertility throughout their life.

Although it is true that men do not go through a menopause and produce sperm throughout their lives, fertility levels of men also decrease with age.

If a female and male partner are both aged 25, the average time to conception is just over 4.5 months. However, this number increases to around 2 years when the male partner is over 40 (and the female partner is 25).

Although sperm is constantly being produced, the quality of this sperm decreases with age. This could be in terms of sperm motility, i.e. how easily the sperm is able to swim towards the egg, or the genetic make-up of the sperm. Children with fathers aged 40 or above are more than 5 times likely to be on the autistic spectrum than children fathered by men aged under 30.

 

Is it all doom and gloom?

Certain lifestyle choices could help increase your chance of getting pregnant.

4Image taken from: kidspot.com.au

This blog may have made it appear that once you reach around 35 you may as well stop trying for a baby.

Of course, this isn’t always the case.

Many couples manage to have happy, healthy children later in life, with little difficulties conceiving.

This is partly down to the specific genetic make-up of that person, for example how quickly their eggs degrade, but there are several environmental factors that can also have an impact on fertility.

Being overweight, smoking, drinking large quantities, and certain STI’s can all reduce fertility in both males and females.

If you’re thinking of waiting till later in life to start a family, make sure you look after yourself. Some studies have shown exercise, and other lifestyle choices to be beneficial in improving fertility.

Find out more here: http://yourfertility.org.au/resource-group/fertility-fact-sheets/

The research: http://www.cell.com/current-biology/abstract/S0960-9822(17)30162-8?_returnURL=http%3A%2F%2Flinkinghub.elsevier.com%2Fretrieve%2Fpii%2FS0960982217301628%3Fshowall%3Dtrue

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