The guide will introduce the fundamentals of male fertility: sperm, semen, reproductive anatomy, sexual health, and hormones. It will also review what affects those elements, and what you can do to protect and improve your fertility.
In the simplest of terms, male fertility refers to a man’s ability to create a pregnancy through sex with a female partner. “Subfertility” means that conception takes longer than normal, indicating that one or both partners may be less fertile than the ideal. “Infertility” is diagnosed when a couple has been having unprotected sex for 6–12 months (depending on their ages) without a pregnancy. Approximately 30–50% of infertility cases are due to issues with male fertility.
An important note: Being subfertile or even infertile doesn’t mean you’ll never be able to get your partner pregnant. In many cases, lifestyle changes or medical intervention can help improve male fertility and achieve pregnancy.
This is the measure of how many sperm are present in the semen. Sperm count refers to the total number of sperm, while sperm concentration refers to the number of sperm per milliliter of seminal fluid. A healthy sperm concentration is 15 million per milliliter or more.
Sperm must be able to travel within the female reproductive system in order to reach and fertilize the egg. This term refers to how many sperm are moving; it’s expressed as a percentage of total sperm. A healthy semen sample has at least 40% motile sperm, and has at least 32% progressive motility—meaning that the sperm are not just moving, but moving in a helpful way (straight lines and large circles).
This measurement tells us what percentage of sperm have the proper shape, size, and structure (a smooth oval head with a cap, a midpiece or “neck,” and a long tail). All sperm-producing people will have some abnormal sperm; in fact, morphology measurements as low as 4% are still considered normal.
The one sperm quality parameter that’s not measured in a typical semen analysis is genetic health. Sperm are “gametes,” male sex cells that exist to carry DNA to the egg. When a sperm combines with the egg, which contains its own genetic material from the mother, they create a unique genetic makeup that drives the development and characteristics of the offspring. So, if the DNA inside the sperm is damaged or abnormal, it’s less likely to be able to fertilize an egg or create a healthy pregnancy.
The presence of abnormal genetic material inside a sperm is called “sperm DNA fragmentation.” The percentage of sperm with fragmented DNA can be measured through a few more complex tests, such as the TUNEL, an alkaline comet test, or a sperm chromatin structure assay (or SCSA). Each of these tests identifies breaks in the DNA inside a sperm cell in a different way, and has different parameters for what’s considered normal.
Male fertility requires that the complex system of glands and ducts that create sperm, produce semen, and transport both out of the body be in good working order. Issues with or abnormalities of these structures can impede fertility.
Typically, during male orgasm, sperm is transported out of the testicles via the vas deferens, to be combined with semen in the prostate; the semen is then carried out of the body via the urethra in the penis. A blockage in the vas deferens—or not having a vas deferens at all, known as congenital absence of the vas deferens (CAVD)—can result in semen with little or no sperm in it. A semen analysis with low sperm count is one clue to this condition.
Age impacts all aspects of male fertility. Studies indicate that normal sperm morphology declines 0.2–0.9% per year of age, or a 4–18% decrease over 20 years. Additional research revealed decreases in motility of 0.17–0.6% decrease per year, resulting in a 3–12% decline in motility between age 20 and age 40. It’s also been shown in some reports that sperm count/concentration decreases with age, though this result is less consistent.
The genetic health of sperm is also impacted by age. Evidence shows that DNA fragmentation is more common the older you get. Every 8 months of a man’s life introduces a new genetic mutation into his sperm.
Other male fertility factors are affected by age as well: semen has lower levels of important nutrients with age, testosterone levels decrease over time, and the incidence of erectile dysfunction increases with age, according to research. So, while male fertility never really “ends” the way female fertility does (at menopause), and sperm are created daily from puberty until death, it certainly becomes more difficult to achieve a healthy pregnancy as you age.
What you eat and how you move is associated with sperm health. In addition, being overweight or obese is associated with lower male fertility.
The common “Western” diet—high in fried foods, refined grains, and red meat—correlates with reduced sperm count, motility, and morphology; diets high in processed meats are associated with lower sperm morphology, while diets high in added sugars are also associated with lower progressive sperm motility. The best diet for male fertility is rich in fruits and vegetables, nuts and seeds, and fatty fish, research shows. Learn more about diet and sperm health.
Physically active people have been shown to have improved sperm motility and morphology, as well as healthier hormone profiles for male fertility, when compared to their more sedentary counterparts. But you don’t need to become a marathoner to improve your fertility. One study found that you can improve male fertility by adopting the simple habit of walking or jogging most days of the week. Learn more about exercise and sperm health.
High alcohol consumption is associated with decreased sperm health, with negative impacts on all sperm parameters. Habitual binge drinking is especially detrimental to male fertility—in one study, men who drank more than 40 drinks per week had a 33% reduction in sperm concentration compared to men who drank fewer than 5 drinks per week. Learn more about alcohol and sperm health.
According to the American Society for Reproductive Medicine (ASRM), infertility rates among smokers are twice as high as among non-smokers. Smoking affects all aspects of male fertility, including sperm count, motility, and morphology. Additionally, smoking damages the genetic health of sperm. The good news is that, if you quit smoking, your fertility can improve fairly quickly—in one follow-up study, sperm motility and morphology began to return to normal within six months of quitting. Learn more about smoking and sperm health.
One option to preserve fertility is to freeze your sperm at their healthiest, youngest state. Sperm freezing ensures that your healthy sperm can be used in the years to come, as your natural fertility decreases with age. It also preserves your parenthood options in the event that an illness or accident threatens your fertility. Scientific research tells us that sperm can be frozen indefinitely with no loss in quality.
Learn more about sperm freezing.