When it comes to fertility and age, the conversation almost always centres on women. Egg quality, ovarian reserve, the "biological clock" are everywhere. Meanwhile, the male side of the age equation isn't focused on nearly as much (if at all).
But male fertility does change with age and if you or your partner is in their late 30s or 40s and thinking about having a baby, it's worth understanding what that means so you can make informed decisions.
Sperm Doesn't Have an Expiry Date, But It Does Change
Unlike eggs, which are present from birth, sperm is produced continuously throughout a man's life. This has led to a cultural assumption that male fertility is basically timeless but not that simple.
After around age 35–40, research shows gradual but sigificant changes in sperm quality, particularly in motility and DNA fragmentation.
Motility refers to how well sperm swim. Sperm that move poorly are less likely to reach and fertilize an egg. Studies show motility declines progressively with age.¹
DNA fragmentation is the one that doesn't get talked about enough. As men age, sperm are more likely to carry damaged DNA, which are breaks or errors in the genetic material inside each sperm cell. High DNA fragmentation is associated with lower fertilization rates, higher rates of miscarriage, and in some research, developmental concerns in offspring.² A standard semen analysis doesn't typically test for this, which is part of why it flies under the radar.
What the Research Says
A large study published in Fertility and Sterility found that men over 45 took significantly longer to achieve pregnancy with their partners compared to men under 25, regardless of the female partner's age.³ Another study found that the risk of pregnancy loss increases with paternal age — with a notably higher risk after age 40.⁴
These aren't reasons to catastrophize. Plenty of men father healthy children in their 40s and beyond, but the idea that male fertility is age-proof is a myth worth correcting.
Signs Worth Paying Attention To
Age-related fertility changes are usually silent since there are no obvious symptoms. That's exactly why proactive testing matters. A few things worth discussing with a doctor if you're in this age range and thinking about conceiving:
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A baseline sperm analysis — either at home (like the Ovry Male Fertility Test) or at a clinic (full picture including motility and morphology)
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Sperm DNA fragmentation testing — not standard, but increasingly available and worth asking about if you've experienced unexplained infertility or recurrent pregnancy loss
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Hormone levels — testosterone naturally declines with age and can affect sperm production; a simple bloodwork panel can flag this
The Lifestyle Piece Still Matters
The good news: lifestyle factors continue to influence sperm health at any age. Sleep, diet, exercise, avoiding excessive heat and quitting smoking all have beneficial effects on sperm quality and those effects can show up within a few months, since sperm takes roughly 74 days to mature. This means the choices made today have a direct impact on the sperm available three months from now.
Sources
- Kidd SA, et al. "Effects of male age on semen quality and fertility." Fertility and Sterility, 2001.
- Moskovtsev SI, et al. "Age-related decline in sperm DNA integrity." Urology, 2006.
- Hassan MAM & Killick SR. "Effect of male age on fertility: evidence for the decline in male fertility with increasing age." Fertility and Sterility, 2003.
- Sartorius GA & Nieschlag E. "Paternal age and reproduction." Human Reproduction Update, 2010.