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It's not just women who have to consider their age when planning a family. Credit: rawpixel
Women are regularly reminded of their biological clock. It turns out that men must also pay attention to their age when it comes to starting a family.
A new study published today in the British Medical Journal Provides convincing evidence that children – and pregnant mothers – are more likely to have health problems when fathers are older.
The fertility of men decreases with age, but not as much as that of women. Men can continue to father children later, as Mick Jagger and other famous fathers demonstrate.
But it takes longer to get pregnant. A study of European men showed that the chances of conception after 50 years of having tried at age 35 were 50% lower than for men under 25 years of age.
In addition, women who have a partner aged 35 or older are more likely to have a miscarriage than women with a younger partner.
High probability of premature birth
The latest study shows that the risks of pregnancy and childbirth problems also increase when fathers are older.
Researchers at Stanford University in California analyzed data from all 40 million live births in the United States between 2007 and 2016 to determine how far the father's age had a impact on outcomes for the infant and the mother.
As the father's age increased, the chances for the baby to be born prematurely, to have low birth weight or to require medical intervention after childbirth, as a assisted ventilation, admission to neonatal intensive care or antibiotics.
When fathers were aged 45 or older, the risk of premature birth was 14% lower for their children (less than 37 weeks) and the risk of low birth weight (less than 2.5 kg) was 14% higher than that of an elderly father. 25 to 34 years old.
Infants whose father was 45 years of age or older were also 14% more likely to be admitted to a neonatal intensive care unit and 18% more likely to have seizures.
If the father was 55 years old or older, newborns also tended to have fewer results in the Apgar test used to assess a child's health status at birth.
These effects were present after adjusting for maternal age, smoking, race, education, and number of prenatal visits.
Future risk of illness
These latest findings add to previous studies showing that the father's age was linked to various health problems affecting offspring.
Danish scientists have calculated the risk of congenital problems associated with older paternity and have shown that several conditions are more frequent. These include rare developmental conditions such as achondroplasia (dwarfism) and cleft palate.
Cancer rates in children also seem to increase with the age of fathers.
The most worrying impact is undoubtedly neurodevelopment and mental health. The offspring of elderly fathers are at increased risk for schizophrenia, mental retardation and autism spectrum disorders.
The risk of schizophrenia increases by 47% when fathers are over 45 years old.
The rate of infantile autism increases by 80% when dads conceive after 45 years.
So what's going on?
Changes in sperm of older men are likely to contribute. The number of DNA mutations containing defective spermatozoa is steadily increasing every year as men get older. These result from exposure to radiation, environmental toxins, alcohol and tobacco.
Aging itself results in less testosterone and a decrease in the number and function of testicular cells.
However, genetics is not the complete explanation. In particular, the increased risk of psychiatric illness does not appear to be due to spontaneous mutations of sperm DNA. Although mutations contribute, they only account for about 10% to 20% of the effect.
Another possibility is that genetic risk factors that are naturally more prevalent in men destined to be older fathers are transmitted to their offspring, rather than new mutations.
Mothers also at risk
The latest data has shown the negative effects of paternity delay not only for infants but also for pregnant women.
The risk of gestational diabetes in pregnant women has increased depending on the age of the father, with women having the child of a man aged 55 or older with a 34 gestational diabetes risk % higher.
The researchers estimate that about 13% of premature births and 18% of gestational diabetes cases in pregnancies associated with older fathers were attributable to the father's advanced age.
This is difficult to reconcile with a genetic explanation. Other biological effects of seminal fluid on the health of pregnancy may be attributable.
The female immune system responds to seminal fluid by generating immune tolerance, which protects against inflammatory exposures that can harm the fetus. Human seminal fluid contains signals known to stimulate the immune response of women, but it is not yet proven that these factors decrease with men's age.
What does all this mean for men who are considering paternity?
Most older fathers do not have fertility problems and can father babies without serious physical or developmental problems.
Overall, the age of the father is much smaller than that of the mother and, in general, pregnancy disorders and infant health problems are rare. Current research does not justify discouraging older men from becoming fathers.
But the medical community needs to do a better job of communicating to couples an understanding of the risks of the advanced paternal age.
More importantly, we need to include men in discussions about pregnancy planning and pre-conception care, to ensure that all couples have the best chance of raising a healthy child.
Explore further:
Reports of studies on older fathers associated with increased risk for birth
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