As Lily Allen's fertility comments spark debate...experts blame older MEN for increasing infertility, as research shows sperm begins to 'mutate' after 25

It is a fact of life that haunts most child-free women under 30: between 35 and 40, your fertility declines dramatically.

Aged 30, there is roughly a one in five chance of getting pregnant per cycle. By 40, this drops to one in 20. 

It is one reason why many women choose to have families earlier than they'd like, sometimes putting careers on hold.

Popstar Lily Allen spoke of the impact of this dilemma recently, commenting that her children, who came along when she was 26 and 27, 'totally ruined' her career.

'It really annoys me when people say you can have it all because, quite frankly, you can’t,' the singer told the UK publication, Radio Times.

But experts increasingly say it's not just women who should be worrying about their biological clock.

Popstar Lily Allen made headlines recently for claiming that women can't 'have it all' when it comes to babies and career

'For far too long, there has been a commonly accepted falsehood that fertility and the biological clock are solely a woman’s issue,' Professor Geeta Nargund, a fellow in the royal college of obstetricians and gynecologists' and founder of Create Fertility, recently told Stylist. 

'The risk of miscarriage for women whose partners are over 45 is twice as high when compared with the rates of those whose partners were under 25.'

Sperm quality and count begins decreasing after age 25 in men, according to a 2015 analysis of 90 studies, comprising over 90,000 participants.  

Yet, much has been said about the increasing rates of infertility in the US and rising maternal age.

According to recent analyses by Pew research, the number of couples seeking fertility treatments in the US has increased 33 percent over the past five years.

Mick Jagger is perhaps one of the most well-known older dads, who welcomed his eighth child with girlfriend Melanie Hamrick aged 73.

Robert De Niro welcomed his seventh child into the world in 2023, at the age of 79 . But experts say famous dads who have kids in their 50s and 60s are misleading the public into believing it's easy and healthy. 

Census data confirms that the number of men and women experiencing infertility has significantly increased over the last 30 years. 

It's true that this is partly due to the age that women now have their first child. In 1990 the median age for the mother at birth was 27, in 2019, it was 30. 

But speaking to DailyMail.com, experts say the rising age of first time dads is a crucial problem that doesn't get enough attention. According to the most recent data, the average age of a new father is also 30 - compared to 27 in 1972.

'The contribution of men being older when they have their first child does have an important impact,' Dr Lisa Webber, an OBGYN from the UK who has been practicing for over 20 years, told DailyMail.com.

 'We shouldn't be just blaming women.' 

A 2021 study from Belgrano University in Argentina found that when the male in a couple was forty or older, there were 20-40 percent more miscarriages than couples where the male was younger than forty. 

For women, we know that generally, fertility becomes complicated with age because the amount of eggs available to fertilize starts to dwindle. 

'For men it’s a slower decline,' Dr. Scott Lundy, a urologist at the Cleveland Clinic, told Forbes. 'As we age, the testicles, like any other organ, don’t function as well as they used to.' 

Scientists point towards a number of factors for men's fertility drop off. Some of which, like loss of libido and erectile dysfunction, are obvious. 

Then there are the molecular contributors. Sperm shape, concentration and agility decrease with age, according to research from the University of Colorado. 

All of which can make it harder for sperm to successfully fertilize an egg.

Also, older sperm tends to have more DNA mutations, which experts say can result in birth defects. 

'Advancing parental age most likely increases the probability of replication errors in the germ line, resulting in an accumulation of mutations,' the Dutch researchers wrote. 

Sometimes, the researchers said, these can then lead to miscarriage. Other studies have also linked sperm DNA fragmentation to pregnancy loss. 

And since DNA fragmentation increases with age, the older the potential father is, the more likely a miscarriage is.

Finally, there are a number of things that can happen over a lifetime that can affect sperm quality - like whether you smoked, caught an STI, or were malnourished. 

Confronting this reality might be uncomfortable, but it's necessary for men to consider, Nargund said. 

'Men who are under the illusion that age will have no impact on their fertility health may struggle to conceive further down the line,' she said. 

'The root of the issue is a lack of education surrounding our own fertility health and the lifestyle choices that affect it, as well as its natural declination with age.'