Does a man’s age affect fertility? What UK couples should know

Most fertility conversations start and end with her age. His age barely gets a mention, partly because men keep making sperm for life and partly because the stories about famous older dads do a lot of the talking. When we were going through IVF ourselves, it was one of the questions we wished someone had answered plainly.

The short answer: yes, a man’s age does affect fertility, but more gradually than a woman’s. From around his late 30s, semen volume, sperm movement and sperm shape tend to drift down, and couples with an older male partner take longer to conceive on average. Most men in their 40s still become fathers. Age is one factor among many, and the everyday habits that look after sperm matter at every age.

This guide covers what the research actually shows, including two large UK studies, what changes in sperm as men get older, and the practical things worth doing if you’re trying to conceive in your mid-30s, 40s or beyond.

Does a man’s age affect fertility?

It does. The NHS infertility page lists age first among the factors that affect fertility, simply saying that fertility declines with age. Most of the public focus is on women because the change is sharper and better understood: eggs are finite, while men produce new sperm continuously.

But “continuously” doesn’t mean “unchanged”. The sperm a 45-year-old makes are, on average, a bit different from the sperm he made at 25, and that shows up in how long it takes couples to conceive.

What the UK research says about male age and time to pregnancy

Separating his age from hers is tricky, because older men often have older partners. The better studies adjust for the woman’s age, and two of the clearest come from the UK:

• The Avon study (Bristol). Researchers looked at 8,515 planned pregnancies in the Avon Longitudinal Study of Pregnancy and Childhood. After adjusting for the woman’s age, smoking, alcohol and other factors, men aged 35 to 39 had about half the odds of conceiving within 12 months compared with men under 25 (Ford et al., Human Reproduction, 2000).
• The Hull study. A survey of 2,112 pregnant women in Hull found that time to pregnancy rose steadily with the man’s age. Compared with men under 25, men over 45 were 4.6 times more likely to have taken more than a year to conceive, and the pattern held even when the women were young (Hassan and Killick, Fertility and Sterility, 2003).

“Taking longer” is the key phrase. These couples did conceive; the studies were of pregnant women. Age tends to stretch the timeline rather than close the door.

What changes in sperm as men get older?

The biggest review on this pooled 90 studies and 93,839 men (Johnson et al., Ageing Research Reviews, 2015). With age, they found significant declines in:

• Semen volume, the amount of fluid per sample.
• Motility, how well sperm swim, including progressive (forward) movement.
• Morphology, the percentage of normally shaped sperm.
• DNA integrity, with a higher share of sperm showing fragmented DNA.

Interestingly, sperm concentration (how many sperm per millilitre) did not fall with age in that review. An earlier review in Fertility and Sterility came to the same conclusion and put rough numbers on it: comparing 30-year-old and 50-year-old men, semen volume was likely to be 3 to 22% lower, motility 3 to 37% lower and normal forms 4 to 18% lower (Kidd et al., 2001).

If you’ve had a sperm test and want to know what those words mean on your own report, our guide to semen analysis in the UK walks through each number.

At what age does male fertility start to decline?

There isn’t a cliff edge. The changes are gradual, and the UK studies above start to see a difference in time to pregnancy from the mid-30s, with a clearer effect after 40 and especially after 45. The reasons are a mix of normal ageing in the testes, more time for lifestyle and health factors to build up, and a higher chance of conditions such as diabetes or high blood pressure, and the medicines used for them.

It’s also worth knowing what’s outside his control and what isn’t. A birthday can’t be changed. Weight, smoking, alcohol, sleep and heat exposure can, and they tend to matter more as the years add up.

Does the father’s age affect pregnancy and the baby?

This is the part people find most worrying, so it’s worth being calm and precise.

• Miscarriage. A 2020 review of ten studies, all adjusted for the mother’s age, found a modestly higher miscarriage risk with older fathers. Compared with fathers aged 25 to 29, the risk was about 1.23 times higher at 40 to 44 and 1.43 times higher at 45 and over. The authors note the effect is smaller than the effect of maternal age (du Fossé et al., Human Reproduction Update, 2020).
• New genetic changes. A whole-genome study of Icelandic families found that each extra year of the father’s age added about two new mutations on average to the child’s DNA (Kong et al., Nature, 2012). Most of these changes are harmless, and most children of older fathers are born healthy.

None of this is a reason to panic or to rule out having a family later. It is a reason to take his side of preconception seriously rather than leaving it all to her.

What can older men do to support their fertility?

Sperm take roughly two and a half to three months to develop, so changes you make today show up in the sperm made over the next 90 days or so. That’s the window we plan around. The basics:

• Weight. The NHS notes that a BMI of 30 or over reduces fertility. Even modest loss through food and movement helps your overall health.
• Smoking and vaping. Stopping smoking is one of the clearest wins for sperm health. NHS Stop Smoking services are free.
• Alcohol. The NHS advises men to stay within 14 units a week, spread over several days. Our caffeine and alcohol guide has the numbers for both partners.
• Heat. Testes work best slightly cooler than the rest of the body. Keep laptops off your lap, go easy on long hot baths, saunas and hot tubs, and choose looser underwear.
• Sleep and stress. Short nights and constant pressure tend to knock libido and routine. Our stress and fertility guide looks at what the evidence says.
• Medicines and health checks. Some medicines can affect sperm. Don’t stop anything prescribed, but ask your GP or pharmacist whether anything you take is relevant while you’re trying to conceive.
• Timing. The NHS suggests sex every 2 or 3 days through the cycle, which keeps things simple and avoids long gaps between ejaculations.

For a fuller 90-day plan, our guide to supporting sperm health naturally in 90 days goes step by step, and the complete guide to male fertility covers the science in more depth.

When should an older man get his fertility checked?

The NHS says to see a GP if you haven’t conceived after a year of trying, or sooner if she is 36 or over or either of you already knows about a possible fertility problem. Our guide on how long to try before seeing a GP has the NHS and NICE timings.

It’s worth going together. A semen analysis is simple, usually arranged through the GP, and it means his side of the picture is checked at the same time as hers rather than months later. See your GP sooner if you notice a change in erections or ejaculation, pain or a lump in the testicles, or if you’ve had testicular surgery, an undescended testicle or cancer treatment in the past.

Where nutrition and supplements fit

No supplement turns back the clock, and nothing here replaces a GP, a semen analysis or the lifestyle basics above. What good nutrition can do is make sure the body isn’t short of the nutrients reproduction relies on during the 90-day window.

• Zinc contributes to normal fertility and reproduction. Shellfish, meat, dairy, beans and seeds are good food sources.
• Selenium contributes to normal spermatogenesis, the process of making sperm. Brazil nuts, fish and eggs provide it.
• Zinc and selenium both contribute to the protection of cells from oxidative stress.
• Folate and vitamin B12 have a role in the process of cell division, which matters when your body is making new sperm every day.

This is where our own formula comes in, gently. Yan, our resident science nerd, built Him Fertility for men in the preconception window, especially men who are a little further along than they planned to be. It brings zinc and selenium together with CoQ10, acetyl L-carnitine, lycopene, astaxanthin and KSM-66 ashwagandha in one daily routine of four capsules, so you’re not managing a cupboard of separate tubs. If you’re both getting ready, the Him & Her Fertility Bundle lets you start on the same day, and you can see everything on our fertility support page.

It’s a food supplement, not a medicine. It sits beside the things that matter most: food, sleep, moving more, and a GP when you need one.

Male age and fertility: frequently asked questions

Does a man’s age affect fertility?

Yes, but more gradually than a woman’s. From the late 30s, semen volume, sperm movement and sperm shape tend to decline, and UK studies show couples with older male partners take longer to conceive on average. Many men still become fathers in their 40s and beyond.

At what age does male fertility decline?

There is no single cut-off. UK research starts to see longer times to pregnancy from the mid-30s, with a clearer effect after 40 and especially after 45. The change is gradual rather than sudden.

Can a man in his 40s or 50s still get someone pregnant?

Yes, many do. Men produce sperm throughout life. Older age is linked with taking longer to conceive on average, so it helps to look after the lifestyle basics and to see a GP if you haven’t conceived after a year of trying.

Does a father’s age affect the baby?

Research links older fathers with a modestly higher risk of miscarriage and with more new genetic changes in the child’s DNA. Most of these changes are harmless and most children of older fathers are born healthy. If you have concerns, talk to your GP before trying.

Can older men improve their sperm health?

Age can’t be changed, but weight, smoking, alcohol, heat and sleep can, and new sperm take about three months to develop. Nutrients such as zinc, which contributes to normal fertility and reproduction, and selenium, which contributes to normal spermatogenesis, can support a preconception routine alongside those habits.

Read our complete guide: Male & female fertility: the complete UK guide