When couples are trying to conceive after 35, much of the conversation tends to focus on female fertility factors—and there are good reasons for that emphasis. But male factor fertility contributes to approximately 40–50% of cases where couples have difficulty conceiving, making it an equally important part of the picture. Understanding how sperm health works, how age affects it, and when evaluation is worthwhile can support a more complete approach to fertility.
According to research reviewed by the National Institute of Child Health and Human Development (NICHD), male infertility is a significant contributor to conception difficulties and is often underdiagnosed because the focus of evaluation may initially be directed at the female partner. A semen analysis is one of the most straightforward first steps in understanding fertility for a couple trying to conceive.
Key Parameters of Sperm Health
Sperm health is assessed across several parameters, each of which contributes differently to fertilisation potential. Understanding these terms can be helpful when reviewing semen analysis results with a healthcare provider.
Count, Motility, and Morphology
The three primary parameters in a semen analysis are sperm count (the total number of sperm per millilitre of semen), motility (the percentage of sperm that are moving and moving effectively), and morphology (the proportion of sperm with normal shape). World Health Organization reference values define lower reference limits for each: at least 16 million sperm per millilitre, at least 42% total motility, and at least 4% normal morphology under the WHO 2021 criteria. Values below these thresholds do not preclude natural conception but may be associated with reduced fertility.
DNA Fragmentation
DNA fragmentation—damage to the genetic material within sperm—is a parameter not captured in standard semen analysis but is increasingly discussed in fertility contexts. Higher sperm DNA fragmentation rates are associated in some research with reduced fertilisation rates, lower embryo quality, and higher miscarriage risk. Testing for DNA fragmentation is not routine but may be considered when standard semen parameters are borderline or when a couple has experienced recurrent pregnancy loss.
Does Male Age Affect Sperm Quality?
Unlike female fertility, which is more clearly tied to a defined timeline of egg reserve decline, the relationship between male age and fertility is more gradual and less absolute. Men continue producing sperm throughout their lives, but research indicates that sperm quality—particularly motility and DNA integrity—does show some decline with advancing age. Studies have found associations between paternal age over 40–45 and modest increases in DNA fragmentation, as well as some associations with reduced pregnancy rates in couples where the male partner is significantly older.
For couples where the male partner is over 40, discussing a semen analysis as part of an overall fertility evaluation is a reasonable step—particularly if conception has not occurred after several months of trying. For context on how a complete fertility evaluation is structured, see our guide to fertility evaluations after 35.
Lifestyle Factors and Sperm Health
Several lifestyle factors are consistently associated with sperm quality in the research literature. Smoking is linked to reduced sperm count and motility, and cessation is supported by evidence as beneficial. Excessive alcohol consumption has been associated with hormonal disruption and reduced semen quality in some studies. Scrotal temperature affects sperm production—the testes are positioned outside the body for temperature regulation reasons—and prolonged exposure to heat (hot tubs, saunas, laptop heat) may have temporary negative effects on sperm parameters in some individuals.
Anabolic steroids and testosterone supplements suppress the body’s own hormone production and can cause significant and sometimes prolonged reductions in sperm count. If a male partner is using or has recently used these substances, this should be disclosed to a fertility specialist. Overall physical health, body weight, and management of chronic conditions such as diabetes and hypertension are also associated with sperm health and are relevant areas to discuss at a healthcare appointment.
When to Seek a Semen Analysis
Most fertility guidelines recommend that both partners be evaluated when a couple has been trying to conceive for twelve months without success (or six months for women over 35). However, a semen analysis can be requested earlier—it is a relatively simple, non-invasive test and provides useful information regardless of how long a couple has been trying. Given that male factor contributes to roughly half of fertility difficulties, early evaluation of both partners avoids the common scenario of delayed diagnosis when female testing is prioritised first.
Frequently Asked Questions
Can male fertility improve with lifestyle changes?
Some research suggests that sperm parameters may improve over 2–3 months (the approximate lifespan of a sperm production cycle) following positive lifestyle changes such as smoking cessation, reduced alcohol intake, and management of underlying health conditions. However, results are variable and depend on the underlying cause of any suboptimal parameters. A urologist or andrologist can advise on which interventions may be most relevant to a specific situation.
What does a semen analysis involve?
A semen analysis involves providing a semen sample—typically by masturbation into a sterile container—either at a clinic or at home within a defined time window. The sample is analysed under microscopy for count, motility, morphology, and other parameters. Results are usually available within a few days. A second analysis is often recommended if initial results are abnormal, as sperm parameters can vary between samples.
Does paternal age affect the baby’s health?
Some research has explored associations between advanced paternal age and certain health outcomes in offspring, including a modest increase in the rate of new genetic mutations (de novo mutations) in sperm. The absolute risk increase associated with paternal age remains relatively small, and most children born to older fathers are healthy. If you have specific concerns about paternal age and genetic risk, a genetic counsellor can provide more tailored information.
Can varicocele affect fertility, and is it treatable?
Varicocele—an enlargement of the veins within the scrotum—is one of the most common identifiable causes of male factor fertility difficulties and is found in a proportion of men with abnormal semen parameters. Treatment (typically a minor surgical or minimally invasive procedure) may improve sperm parameters in some cases, though outcomes vary. A urologist or reproductive specialist can assess whether varicocele is present and whether treatment is appropriate.
Key Takeaways
- Male factor contributes to approximately 40–50% of fertility difficulties; evaluating both partners early avoids delayed diagnosis.
- A semen analysis measures sperm count, motility, and morphology—values below reference ranges may indicate reduced fertility but do not rule out natural conception.
- Male fertility does decline gradually with age, with some research showing associations between paternal age over 40–45 and reduced sperm DNA integrity.
- Lifestyle factors including smoking, alcohol, heat exposure, and anabolic steroid use can affect sperm quality and are worth addressing before conception.
- Seeking a semen analysis after six months of trying (alongside female evaluation) is appropriate for couples where the female partner is over 35.
Medical Disclaimer
This content is for informational purposes only and does not constitute medical advice. Individual health situations vary significantly. Always consult a qualified healthcare provider before making decisions related to your health, fertility, or pregnancy.
About the Author
Emily Carter is a women’s health writer focused on fertility, pregnancy after 35, and sleep changes in midlife. She writes research-informed, non-alarmist content to help women navigate reproductive and hormonal transitions with clarity and confidence.