Aging; Men's Health; Your Pregnancy Matters

How does a father’s age affect fertility and a baby’s health?

Aging; Men's Health; Your Pregnancy Matters

Men are waiting longer to have children in the U.S.

Legendary actors Robert De Niro and Al Pacino created a baby buzz in Hollywood when both welcomed newborns into their lives at the advanced ages of 79 and 83, respectively.

While the “The Godfather” duo may be taking the older dad trend to the extreme, the age at which many men are becoming fathers in the U.S. has increased by 3.5 years – from an average of 27.4 years to 30.9 years between 1972 and 2015. About 9% of all births in the U.S. are connected to men over 40.

Though men’s “biological clocks” don’t tick as loudly as women’s, they do count down, which means a father’s age can influence fertility and the health of their future children.

There has been extensive research about infertility and pregnancy complications in maternal age – far fewer studies have explored similar reproductive factors in men. In fact, literature doesn’t even agree on what age is considered “advanced” for men. For women, it’s 35 but for men it can range from 35 to 50.

Still, there is growing evidence that advanced paternal age is associated with increased difficulty conceiving and increased susceptibility in children to a range of conditions.

How does aging impact male fertility?

Several studies have shown fertility rates decline as a man ages. A 2020 study found that conception is 30% less likely for men older than 40 than it is for men younger than 30.

There are several reasons for this, including that semen volume, total sperm count, and sperm motility (how well the sperm can move toward the egg) all decrease as men age. Many potential age-related factors contribute to these changes, such as:

  • Declining testosterone levels
  • Decreasing blood supply to the pelvic area
  • Shrinking or softening testicles
  • Benign prostatic hyperplasia (BPH, or enlarged prostate)
  • Narrowing of the vas deferens, which are the tubes that move sperm from inside the testicles

If you are concerned about whether age has affected your fertility or your partner’s, the UT Southwestern Male Infertility Clinic can conduct a semen analysis to measure sperm volume, motility, and shape. Based on the results, our specialists can recommend further testing or develop a personalized fertility plan that may include:

  • Fertility treatment such as in vitro fertilization or intrauterine insemination
  • Microsurgery to repair or unblock the vas deferens
  • Sperm banking
  • Testosterone therapy
  • Treatment for erectile dysfunction

Related reading: Male infertility: Treating the physical and emotional side effects

Can aging cause genetic mutations in sperm?

A woman is born with all the eggs she’ll ever have. But a man is constantly making new sperm cells that divide and replicate about every 16 days. By age 20, a man’s sperm cells have gone through about 150 divisions. That number could grow to 800 by the time he is 50.

The more times sperm cells replicate, the more chances there is for a genetic mutation to occur. Fortunately, most genetic mutations are benign, meaning they won’t cause any harm to a baby.

Examples of genetic conditions that have been associated with advanced paternal age include some skeletal dysplasias or dwarfism syndromes. These include achondroplasia, the most common form of dwarfism, and thanatophoric dysplasia. Some types of craniosynostosis syndromes have also been associated with advanced paternal age. These cause the premature fusion of bones in the skull, which affects head shape, and include Crouzon syndrome, Pfeiffer syndrome, and Apert syndrome.

These conditions are caused by genetic variations (or mutations) in specific genes. They are sometimes inherited but can also occur sporadically and unpredictably. One factor correlated with this sporadic genetic variation in some cases is paternal age.

We routinely offer testing during pregnancy for conditions associated with maternal age, such as Down syndrome, but with 20,000 human genes, there are just too many potential genetic mutations associated with paternal age to check all of them. Talk with a doctor or genetic counselor about your unique situation and whether genetic testing may be appropriate.

What other conditions are associated with paternal age?

A father’s age can also affect a baby’s health at birth and later in life. One study revealed that babies who are born to men 45 or older were 14% more likely to be admitted to the neonatal intensive care unit (NICU), 14% more likely to be born premature, 18% more likely to have seizures, and 14% more likely to have a low birth weight.

The same study also found that pregnant women whose partners are 45 or older are 28% more likely to develop gestational diabetes, which can lead to a larger baby, low neonatal blood sugar, premature birth, and increased risk of developing type 2 diabetes later in life.

Research has shown a connection between advanced paternal age and several childhood cancers, such as leukemia and non-Hodgkin lymphoma, and a range of psychiatric and neurological disorders, such as schizophrenia and autism spectrum disorders. However, these diseases are multifactorial, which means they are caused by a complex combination of genetic and non-genetic factors, including environmental and lifestyle factors.

Having an older father does not mean a baby will automatically develop any of the conditions listed above. Although advanced paternal age does bear some risk, there is a very low likelihood that becoming a father late in life will adversely impact the future health of your baby.

If you have questions, though, talk with your health care provider and a genetic counselor. We can help you understand the risks and recommend any tests or procedures that are available to increase your chances of a healthy pregnancy and baby.

To visit with a provider or genetic counselor, call 214-645-8300 or request an appointment online.