The increasing number of men waiting until they are 40 or 50 to have children could lead to a wave of premature, low-birth-weight and unhealthy babies.
In recent decades, America has been experiencing a so-called baby boom, and the conversation has focused on the fact that women are increasingly waiting until they’re too old to give birth, a new study finds.
But men also appear to have a “biological clock” that ultimately leads to fertility problems, according to the team from Stanford University, Emory University and the University of Rome.
They found a link between fathers in their 40s and 50s and a number of increased risks at birth beyond low birth weight and preterm birth. They also found respiratory problems, seizures and autism spectrum disorders.
In 2011, fathers aged 50 and older accounted for 1.1 percent of all births in the U.S. By 2022, that share had risen to 1.3 percent. The largest increase occurred among fathers aged 50 to 54, whose share of births grew from 0.7 percent in 2011 to 0.9 percent in 2022.
Older paternal age is associated with an increased risk of adverse birth weight outcomes, including low birth weight. Image courtesy of the journal Frontiers in Endocrinology
The average age of all fathers rose steadily from 30.8 in 2011 to 32.1 in 2022, and the share of births where only fathers were 50 or older rose from 1.1 percent to 1.3 percent from 2011 to 2022.
Researchers from the US and Italy looked at more than 46 million live births in America between 2011 and 2022, with the father’s age recorded in 85 percent of births.
Most fathers were under 50, with an average age of around 31. Just over one percent of births were fathered by men aged 50 or older, with an average age of 53.8 in that group.
The researchers used birth data to examine the association between paternal age and pregnancy outcomes, as well as the effects on maternal health.
Fathers between the ages of 50 and 59 were 16 percent more likely to have a premature baby and 14 percent more likely to have an underweight baby, compared with fathers in their 30s.
There was also a 13 percent higher risk that fathers would develop gestational diabetes later in life.
Fathers in their sixties were also more likely to have their mothers develop gestational diabetes. However, this risk did not apply to men in their seventies.
Men in their 70s who became fathers were 21 percent more likely to have a premature baby and 24 percent more likely to have an underweight baby, compared with younger fathers.
They also found that older fathers in their 50s were twice as likely to need help conceiving a child using assisted reproductive technology (ART) – any type of reproductive treatment or procedure, such as IVF, used to become pregnant.
However, it is not yet clear whether this has actually led to an increase in babies being born with conditions such as low birth weight, breathing problems, seizures and genetic abnormalities.
The researchers added: ‘These associations increased as paternal age increased, with fathers aged 70 and over being more than six times more likely to be using ART.’
Their findings were published in the journal JAMA Network Opened.
The link between autism and paternal age has been studied for decades, with many large-scale studies using government health databases and thousands of birth certificates
Male fertility generally declines as they age. This is due to a series of factorssuch as a decrease in sperm volume of up to 3.3 percent per year, the inability of sperm to swim, and changes in the structure and shape of sperm.
While women are born with all the eggs they will ever have, men continuously produce new sperm cells that divide and multiply approximately every 16 days.
Each time these cells divide – which can happen about 800 times by the time a man is 50 – it increases the chance of a genetic mutation occurring.
And a wide range of genetic disorders are associated with increased paternal age, including some skeletal abnormalities such as achondroplasia, the most common cause of dwarfism.
Older paternal age has also been associated with conditions caused by an abnormal fusion of one or more joints between a baby’s skull bones.
This can lead to an abnormal shape of the head and increased pressure in the skull, which can hinder the development of the baby’s brain.
In addition to genetic conditions, older fathers are associated with a higher risk of their children diagnosed with schizophreniaobsessive-compulsive disorder, autism spectrum disorder, and later-onset bipolar disorder.
Research has shown that the chance that the child of an older father will later be diagnosed with bipolar disorder is 37 percent higher than that of a father in his 30s or 40s.
An Israeli study found that the risk of autism in children of men aged 40 or older was more than five times higher than in children of men under 30.
A very influential study In 2018, Stanford University collected data on more than 40 million births. It found that not only are older fathers more likely to have babies who are underweight and premature, but they are also at greater risk of epileptic seizures.
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Compared with fathers between the ages of 25 and 34 (the average age of childbirth in the U.S.), babies born to men 45 or older were 14 percent more likely to be admitted to the neonatal intensive care unit, 14 percent more likely to be born prematurely, 18 percent more likely to have seizures, and 14 percent more likely to be low birth weight.
Fathers aged 50 and older were 10 percent more likely to have their newborn child require ventilation at birth and 28 percent more likely to have their child admitted to the neonatal intensive care unit.
Older fathers are generally associated with wealth and financial stability. Well-known examples include actors Robert De Niro, Al Pacino and Billy Joel. But the researchers found that this is not always the case.
They cited Scandinavian research showing that older fathers come from a variety of urban and rural environments, with varying levels of education, marital status and health literacy.
They added: ‘The trend to delay fatherhood is often attributed to less attention to the male ‘biological clock’ and the desire for educational and financial stability before starting a family.
‘Previous studies have also highlighted the influence of changing gender norms that promote active parental involvement while emphasizing traditional roles such as that of the male ‘breadwinner.’
Women are increasingly postponing childbirth, despite being constantly aware of the presence of this ‘biological clock’, choosing instead to focus on professional growth and financial stability.
