Beyond the biological clock: How paternal age, egg quality and AI are reshaping fertility

For decades, conversations around fertility have fallen almost entirely on women. Early reproductive science and society pressures have reinforced the idea that female age was the only timer that mattered when it came to having a family.

However, new data presented at the recent European Society of Human Reproduction and Embryology (ESHRE) conference shows this long-standing imbalance is finally changing.

The scientific consensus is clear: a father’s age matters. But it’s not just about sperm age in isolation. The relationship between sperm health, egg quality and state-of-the-art Artificial Intelligence (AI) is redefining how we predict and optimise pregnancy success.

Advanced paternal age: How a father’s age over 45 impacts fertility and IVF

While media stories often highlight older famous fathers, science tells a different story. Research shows that a fathers age, specifically 45 years or older, plays a crucial role in both natural conception and fertility treatments like IVF.

Because a man’s body continuously produces new sperm throughout his life, genetic and biological changes build up over time.

Research shows that as a father gets older, several key fertility markers begin to decline:

• Semen quality and motility: There are noticeable drops in overall semen volume, as well as how fast and efficiently the sperm can swim (motility).
• DNA integrity: Older sperm is more likely to carry DNA damage and subtle genetic shifts.
• Impact on IVF and miscarriage: Advanced paternal age can lead to fewer healthy blastocyst embryos reaching the crucial stage needed for transfer, lower overall live birth rates and an increased risk of miscarriage – even when using healthy donor eggs.
• Child health: Long term population studies link older paternal age to a higher risk of neurodevelopmental conditions in children, such as autism spectrum disorders and potential genetic abnormalities. However, it’s important to note that most children born to older fathers do not develop autism.

Egg quality: Nature’s primary repair engine

Despite the measurable impact of male reproductive aging, nature has built a powerful countermeasure. Studies reveal that the negative effects of a father being over 40 to 45 are significantly smaller when the mother is under 36.

Why? The answer lies in the incredible biology of the egg.

A young, high-quality egg is equipped with robust internal repair machinery. Right after fertilisation, the egg actively works to fix damaged DNA strands carried in by the sperm. This natural repair work helps reduce the impact of age-related sperm decline, protecting the embryo’s ability to develop normally and achieve a healthy pregnancy.

While combining a high-quality egg with younger sperm yields peak success, a healthy egg remains the single strongest protective buffer against the effects of an older father’s age.

The AI revolution in reproductive medicine

Understanding the delicate relationship between sperm and egg health requires precise, objective measurement. This is where Artificial Intelligence (AI) comes in.

Egg quality – predicted by maternal age and now measured with increasing accuracy by emerging AI tools – remains the strongest predictor of IVF outcomes. High-quality eggs consistently yield higher fertilisation rates, better embryo development and normal chromosome counts (euploidy), especially when paired with younger sperm.

Importantly, superior egg quality also helps lessen the adverse reproductive effects associated with advanced paternal age.

Shared responsibility, timely action

The message is the same for both men and women: Adopting a healthy lifestyle can improve fertility potential but it cannot pause time.

A nutrient-rich diet, regular exercise and avoiding toxins will always support sperm and egg health, but age remains the single biggest factor in overall success.

The path forward requires moving away from putting all the focus on female age and embracing a shared-partner approach:

1. Seek medical advice as soon as you can: Both partners should be tested early. As well as standard female tests (like ovarian reserve checks), men should consider advanced sperm analysis like DNA fragmentation testing, rather than delaying care.
2. Proactive family planning: Understanding that both partners’ ages play a role gives you the power to make informed choices, whether that means exploring egg or sperm freezing, or starting fertility care earlier.

Seeking medical advice early provides the greatest opportunity to benefit from advances in fertility care and emerging reproductive technologies while they are most likely to make a meaningful difference.

For more information about fertility assessments at CRGH, click here.

Medically reviewed by Mr. Ozkan Ozturk, consultant gynaecologist and specialist in reproductive medicine, CRGH.