Does male fertility decline with age? Do babies born to older fathers have more complications? In this guide, we dive into the emerging research on how the dad’s age impacts outcomes.


Serious considerations abound for couples who wish to delay beginning a family. And while conventional wisdom has centered on the “ticking” of a woman’s biological clock, recent research indicates that men who become fathers past the age of 40 also face risks.

In fact, a 2018 study published in the BMJ (formerly known as the British Medical Journal) involved over 40.5 million births in the United States. Babies born to older fathers faced risks such as premature birth, low Apgar score (a shorthand method of determining a newborn’s risk of infant mortality), seizures, and low birth rate.

The study, directed by Dr. Michael L. Eisenberg, a urologist and head of male reproductive medicine and surgery at Stanford University School of Medicine, reached the conclusion 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.”

Dr. Hilary K. Brown, a researcher in reproductive public health at the University of Toronto, published an editorial that accompanied the BMJ study, stressing that “current findings underscore the importance of including, in reproductive life plans, discussions of paternal age and declines in sperm quality.”

Age of the father and time to conceive 

Another study indicates that a couple’s chances of having a baby decrease as the father ages. Laura Dodge, who headed up the research at the Beth Israel Deaconess Medical Center and Harvard Medical School, told the Guardian that couples should keep the study’s findings in mind when thinking about starting a family.

“When making this decision, [couples] should also be considering the man’s age,” said Dodge.

Complicating matters further for men who’d prefer to wait a few years, the study suggested that some women benefit when trying to conceive with younger men.

Specifically, the Harvard study, reported at the European Society of Human Reproduction and Embryology conference held in Geneva in 2017 (and subsequently published in the journal Science Daily), found that when women aged 35-40 tried to conceive with men aged 30-35, the likelihood of their having a baby was slightly more than one in two chances. This rate increased to seven in ten chances when the man was 30 years of age or younger. Women aged 30 to 35 who had older male partners on average experienced live birth rates of 64%; the rate increased slightly to 70% when they partnered with men in their own age range.

Women aged 30 to 35 who had older male partners on average experienced live birth rates of 64%; the rate increased slightly to 70% when they partnered with men in their own age range.

Nick Macklon, professor of obstetrics and gynecology at the University of Southampton, who did not contribute to the study, noted that the findings could give women ammunition in the battle to motivate their male partners to get moving in a family direction. He cited several studies that show women often wait to conceive because men drag their feet in supporting this decision.

“This reminds us that it takes two to tango and it’s not just down to the age of the woman,” Macklon said.

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What causes male fertility to decline as men grow older? 

Researchers aren’t certain why male fertility declines with age, but they have zeroed in on some factors that come into play when couples are trying to conceive.

Women are born with a fixed number of eggs for life; these can rack up mutations as women age, which helps to explain why older women are more likely to experience problems with fertility. It’s a different story for men. While it’s true that the aging process impacts sperm quality, which in turn makes it more difficult to father a child as well as increasing the risk of miscarriage, Dodge suggests that aging sperm isn’t entirely responsible for male fertility problems.

She theorizes that even though men produce new sperm daily, mutations eventually latch onto the cells that make those. Plus, older sperm tends to be characterized by more damaged DNA. She plans to conduct further work to get to the bottom of these issues.

Harry Fisch, MD, director of the Male Reproductive Center at Columbia-Presbyterian Medical Center in New York, tells WebMD that while it’s true that “[w]omen set the baby-making agenda,” that doesn’t give men a total pass as far as conception is concerned.


This article was contributed by our friends at Legacy. Legacy is the fatherhood company, helping men test or freeze their sperm without having to visit a doctor's office. Incubated at Harvard University, Legacy is run by a team of healthcare and fertility experts who believe in changing the outdated view that fertility is a 'women's issue.' Legacy is available nationwide for men or couples thinking about family planning or fertility preservation.