What’s fair is fair, right? I mean, if women have biological clocks, shouldn’t men?

For centuries, stories have been passed on to admire the seemingly timeless fertility of men. The oldest father documented in the medical literature was George Isaac Hughes. Born in 1840, Mr. Hughes was 94 years young at the time of the birth of his son by his second wife. Much more recent examples include Mick Jagger, whose youngest child was born when he was 73, or George Clooney, who had twins at age 56. With this fertile prowess, do men even have a clock?

So, when people talk about prime childbearing years, they are often referring to a woman’s “biological clock.” Some background first: a woman is born with all the eggs she will have in her lifetime, where men start making sperm at puberty and continue this for the rest of their lives. It’s commonly known that as women age, they have less egg quantity and quality. As a result, they are at a higher risk for infertility, miscarriages and having children with health problems due to chromosomal abnormalities, such as Down’s syndrome.

While women are technically considered fertile until menopause, their monthly odds of pregnancy decline from 20 percent at age 30 to 5 percent at age 40, and decreases from there. These same ages see a miscarriage rate rise from 10 percent to 33 percent, then continue to rise with age.

About 12 percent of women in the U.S. between the ages of 15 to 44 have difficulty getting pregnant or carrying a pregnancy to term, with the cause equally divided between men and women at about 40 percent. In about 33 percent of couples with infertility, both a male and female cause is found.

Age and Male Fertility

Male fertility is even more relevant now. Since the 1970s, the percentage of births to men aged 40 or older in the U.S. has doubled. Since 1980, the fertility rate for men in their 30s has increased by 21 percent and for men aged 40 years and older, the rate has increased nearly 30 percent. In 2015, they accounted for 9 percent of births.

Although men can remain potentially fertile their entire lives, their fertility declines with age and health risks for their children increase. Recent studies are shedding more light on male infertility and how a man’s age can impact the length of time it takes to get pregnant, chances of miscarriage and the child’s health post-birth. Specifically, men above age 40-45 take four times as long to contribute to a pregnancy compared with men under age 25. They also have increased rates of infertility, a higher chance of the mother having a miscarriage, a higher rate of the child having birth defects, twice the chance of having a child with autism, and four to five times the chance of having of a child with schizophrenia.

A recent study of more than 40.5 million births by physicians at the Stanford University School of Medicine concluded that “more than 12 percent of births to fathers aged 45 years or older with adverse outcomes might have been prevented were the fathers younger.”

The study revealed that fathers older than 45 had a 14 percent greater chance than fathers in their 20s and 30s of their babies being born prematurely and at low birth weight. As the fathers’ ages increased, their babies were more likely to need help with breathing and require neonatal intensive care.

How to Make the Most of Male Fertility

Given this concern, let’s review ways for men to protect and maximize their fertility:

Body weight. Higher body mass index (BMI) is linked with decreasing both sperm count and movement. Proper diet and regular exercise can help you maintain a healthy BMI.

Diet. The old adage holds true: be good to your body and your body will be good to you. Choose plenty of fruits and vegetables, which are rich in antioxidants, especially vitamin C, vitamin E and CoQ10, to improve sperm quantity and quality.

Sexually transmitted infections (STIs). Infections like chlamydia and gonorrhea can cause infertility in men by blocking vital ducts that allow passage of sperm. Always practice safer sex.

Manage stress. Stress can cause lower sperm function and sexual performance anxiety – think stage fright! If you are experiencing stress with difficulty conceiving – and who isn’t? – reach out to your partner and/or a counselor for health coping strategies and stress-reduction techniques.

Exercise. Moderate physical activity can have positive or neutral effects on sperm, but intensive exercise can reduce sperm function. There is a sweet spot with exercise intensity.

Don’t smoke. Men who smoke cigarettes are more likely to have impaired sperm and higher rates of genetically damaged sperm. And smoking causes harmful effects to your female partner through second-hand smoke.

Limit alcohol. While there is debate on alcohol’s effect on sperm, prolonged abuse can cause impotence.

Talk to your doctor about medications. Many medications impact fertility, including calcium channel blockers (reduce fertilization), testosterone and anabolic steroids. The latter two can cause azoospermia (no sperm in the ejaculate).

Avoid exposure to toxins. Exposure to environmental toxins, especially phthalates (used in many plastics and hundreds of products), may reduce sperm function.

Stay cool. Because the testes are outside the body, they are sensitive to temperature fluctuations. Increased temperature to the scrotum can impair sperm production. Wear loose-fitting underwear, avoid saunas and hot tubs and limit scrotum exposure to warm objects (such as laptops).