Mick Jagger of the Rolling Stones just celebrated the birth of his eighth child. Experts say late fatherhood has its benefits, but there’s also a lot of risks.

Why would a man in his prime grandparenting years choose to become a new father?

To some extent, the answer is “because he can.”

Every man comes equipped with his own sperm factory and unless it is interfered with by illness, accident, or medication, it stays in production until the end of his life.

Maybe, too, it’s his wife. If she’s considerably younger, she may want a baby.

That’s what seems to have happened in some celebrity families. The latest is the Rolling Stones’ leader singer Mick Jagger, who just became a father again for the eighth time — at the age of 73.

There was no comment from Jagger’s first seven children — Georgia, James, Jade, Elizabeth, Lucas, Karis, and Gabriel — who range in ages from their 40s to their teens.

Fellow Rolling Stone Ron Wood also recently became a father again at 68 after his wife, Sally Humphreys, gave birth to twin girls.

President-elect Donald Trump was 60 when son Baron William Trump was born 10 years ago.

Media mogul Rupert Murdoch was 72 when daughter Grace was born. Murdoch has six children from previous marriages.

Meanwhile, comedian Steve Martin became a father for the first time in 2012 at the age of 67.

Actor Nick Nolte’s girlfriend, Clytie Lane, gave birth to their daughter, Sophie Lane Nolte, when Nolte was 67.

And the late actor Tony Randall was 79 when he became a father.

Read more: Chinese scientists say they’ve created sperm in a lab »

Of course, not everybody can afford to have children later in life.

But the phenomenon is on the rise, according to Men’s Health magazine.

The average age for first-time dads is slightly more than 25 years, according to the Centers for Disease Control and Prevention (CDC). That’s about the same as it was 15 years ago.

However, between 1980 and 2014, there has been a 58 percent increase in the number of men 35 and older becoming fathers, according to the most recent government statistics.

Dr. Dan Williams agrees there’s a trend in American families to delay family planning.

“Both men and women are focused on their careers and plan to have families later,” said Williams, an associate professor of urology at the University of Wisconsin, and president-elect of the Society for Male Reproduction and Urology.

Some people respond by freezing their sperm and eggs.

“The effects of age on fertility are more studied in women,” Williams told Healthline.

Read more: Why young women are freezing their eggs »

Generally speaking, the older the man, the higher the risk, especially with Down syndrome, Williams said.

The difficulties increase when both parents are older. The genetic abnormalities include autism and schizophrenia. There also might be problems conceiving and carrying a baby to term.

Williams noted there have also been some suggestions about certain cancers in children born to men of advanced paternal age, including breast cancer and central nervous system tumors.

Risks vary with the individual, he said. “A man who had great sperm production at 30, even if he loses a little, still has plenty of healthy sperm” at 60.

Williams emphasized, “There is no clear cutoff date” for men. Generally, women are considered “older mothers” after 35.

There is no agreed-upon standard for what constitutes “advanced paternal age.” So doctors in the field of reproductive health can’t specify just when there are high risks.

Nor is there a single test to assess the risk of having a child with problems.

A research team from Sweden studied everyone born in Sweden between 1973 and 2001 (more than 2.6 million children) and compared the risk of various mental health problems in children born to older fathers with that of children born to younger fathers. The researchers also included comparisons between siblings and cousins.

Compared with children born to fathers who were 20 to 24 years old, the children of fathers ages 45 and older were 3.5 times more likely to develop autism, 13 times more likely to develop attention deficit hyperactivity disorder, and 24 times more likely to develop bipolar disorder, the study found.

The children of older fathers were also at higher risk for psychosis, suicide attempts, substance abuse, failing grades in school, and low educational attainment, according to the study, published in 2014 in the journal JAMA Psychiatry.

Read more: Research on ‘three parent’ babies »

Despite these possibilities, in most cases the increasing age is not a cause for concern, the Men’s Health magazine article concluded.

Few of these older dads have fertility problems, and their babies don’t have serious physical or developmental problems, Dr. Robert E. Brannigan, a urologist, and specialist in male reproductive medicine at Northwestern University’s Feinberg School of Medicine, told Men’s Health.

Consider some basic biology and a little math to clarify the picture. Sperm is produced continuously — about 1,000 for each heartbeat, Dr. Bradley Anawalt, a University of Washington endocrinologist, and a spokesperson for the Endocrine Society, told Men’s Health.

However, Dr. Ranjith Ramasamy, director of male reproductive medicine and surgery at the University of Miami Miller School of Medicine, told Men’s Health that after about age 30, some problems arise. These include aging as well as exposure to radiation and environmental toxins.

As a result, men lose both Leydig cells — the cells in the testicles that make testosterone — and Sertoli cells, which support and nurture new sperm.

That means more sperm are defective and contain potentially harmful DNA mutations, known as de novo mutations. According to a paper published in Nature, the average dad under age 30 passes on about 55 mutations to a child. With each passing year, that number increases by two.

So by age 80, the paternal contribution would be eight times as many de novo mutations. One possible consequence is trouble conceiving or carrying a pregnancy to term, Ramasamy said.

Read more: Scientists given OK to use gene editing on human embryos »

Other mutations don’t affect conception or fetal development, but they can cause birth defects, chromosomal abnormalities, or other genetic diseases in children, Ramasamy said.

In a Baylor College of Medicine review, the researchers crunched the numbers on 86 congenital problems linked to older fatherhood.

They concluded that the risk of having any of these issues increased from 1 in 50 among the general population to 1 in 42 among babies born to men age 40 and older.

Specifically, the risk of having a child with achondroplasia — a type of dwarfism — spikes from 1 in 15,000 to 1 in 1,923 once men reach age 50. And the risk of schizophrenia more than quadrupled, from 1 in 100 within the general population to 1 in 22 with fathers over 50.

Beyond parsing the numbers, there’s an incontrovertible biological fact that older people die before younger ones.

As Julianne Zweifel, Ph.D., a clinical professor of obstetrics and gynecology at the University of Wisconsin, told Time magazine, “Even if you’re Paul McCartney’s child, you get ripped off if your father dies when you’re in your early 20s.”