Research shows that the older a mother and a father are when they have a child, the greater the risk of autism. It is unknown why this is or to what degree a parent’s age influences the chance of autism in their child.

Older Fathers & Autism Risk

In 2011, Molecular Psychiatry published a study that found children born to older fathers are more likely to be at risk of developing attention deficit hyperactivity disorder and autism spectrum disorder (ASD) than children born to younger fathers.

The likelihood of a child being born with autism to a father in his 40s is 28% higher than the chances of a child being born with ASD to a man in his 30s. For men in their 50s, the chances of fathering a child with ASD can be as high as 66%. 

Researchers theorized that the sperm of older men has a higher number of mutations, and these mutations might be passed on to their children. This may suggest the nature of the connection between advanced paternal age and the development of ASD in their offspring. Mutations might be more likely to develop as men grow older.

The cells that form sperm duplicate themselves throughout life. After many decades, the duplicated cells (themselves being duplicates of cells) form errors. This is like the quality of a photocopy degrading with every new copy. 

Genetic Marking & Vulnerabilities

Another theory is that genes passed on by older men are not correctly marked. This is the process of establishing from which parent a particular gene comes. Marking also determines whether the gene will be active (like the gene that determines eye color). Errors with the genetic marking process could result in developmental problems in their offspring. Mutations in the sperm composition of an older man may cause these errors.

Even if a man were to take good physical care of himself, with exercise and healthy lifestyle habits, his sperm would still age biologically. The general consensus in the research community is that the older a father is, the greater the chance his children will be at a higher risk of ASD. Multiple studies in different countries have shown a high prevalence of the development of autism spectrum disorder in children who have older fathers.

The age ranges of the men differed across studies, which makes it difficult to know for sure when the chances of fathering a child with autism increases for men. However, researchers observe that those chances increase predictably over time (5% to 10% more likely in the mid-40s, and then rising for every decade afterwards), as opposed to suddenly appearing after a certain age. 

Advanced Maternal Age

When it comes to women, research shows that pregnancy becomes riskier as a mother-to-be gets older. Advanced maternal age has been linked to developmental disorders in offspring, such as Down syndrome. It also affects the likelihood that autism will develop. 

Researchers writing in Autism Research noted that mothers over the age of 40 had a 51% greater risk of having a child with autism compared to mothers who gave birth between the ages of 21 and 29. Mothers over age 40 had a 77% higher risk of having a child with autism compared to mothers 25 and under. 

Past research strongly suggests that both maternal and paternal ages independently connect with the risk of autism in a child. While advanced paternal age can affect the development of autism, advanced maternal age is the bigger risk. 

APGAR Scores & Awareness

Women over the age of 35 are at higher risk of having prolonged labor, premature deliveries, or breech deliveries (when the baby comes out feet first, instead of head first).

Furthermore, giving birth after 35 can result in babies with low APGAR scores, which is a test to determine the baby’s heart rate, muscle tone, and other vital signs to check if the baby needs further medical or emergency care. The APGAR test is done one minute after birth, and again, five minutes after birth. 

Researchers have also noted that older parents might have more awareness of child development based on an increased likelihood of having other children earlier in life. Likewise, older parents tend to be more well informed, and as a group that have a greater awareness of autism and screening for developmental disabilities (or the other risks of having children in their 30s and beyond). Therefore, they might be more likely to go to a doctor if they notice their child is not developing as expected. Education levels and socioeconomic statuses are also factors in women over 30 having access to diagnostic and treatment services for their children.

Environmental Factors & Starting a Family

Investigations into the environmental risk factors implicated in the development of autism are ongoing. And these studies are often focused on factors that pertain to the age of the parents. For example, the older a woman is by the time she gives birth, the higher the likelihood that she has been exposed to environmental or social factors for much longer than a woman who gives birth at a younger age, and these factors could increase ASD risks in later-life pregnancies.

Regional studies have suggested that maternal autoimmunity is a condition where some mothers develop antibodies due to exposure to environmental pollutants. The antibodies increase in number as the woman ages, transferring into the fetus and affecting early brain development. 

Whatever the mechanisms, the relationship between maternal age and autism is highly nuanced. Most experts insist that this should not prevent women from having children at any age.

One specialist told Scientific American that people should start families “whenever it’s right for them,” and parents should focus on being as healthy as possible. Avoiding exposure to pollutants in the environment should be par for the course and not specifically a safeguard against giving birth to an autistic child. 
However, some experts simply say that older parents should be aware of the risks that come with having children. And this includes how the chances of autism spectrum disorder increase with advanced maternal and/or paternal age. 

Transgenerational Factors

Additional research has looked at the age of the grandparents when the parents were born. Researchers identified what they called “potential transgenerational risk for autism spectrum disorder.” This involves how grandparental age at the time of the birth of the parents might affect the future risk of autism in the grandchild.

The implications of this are that young grandparents pass on some degree of risk to their children. This might have some bearing on the chances of their grandchildren developing autism. Grandparents who did not have access to good nutrition could have a detrimental impact on the biology of their children. As these children age, that impacted biology could cause developmental disorders in their own children. 

Such a model complements both the genetic and environmental factors that are believed to be responsible for autism. As with most research in this area, however, wide-scale testing remains challenging. 

Grandparents & the Effect on Autism

The idea that a child’s autism might be related to health concerns their grandparents had presents its own challenges. Some might feel helpless because the factors that determined their child’s ASD were never in their control.

American women are waiting longer to have children but are more likely to have children than women as recently as the 2010s. Given that more people around the world are postponing parenthood,  there is increased interest, and emotional investment, in learning how the age and health of parents — and grandparents — affect autism diagnoses. 

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