Having older parents, a difficult birth, or infections during pregnancy are all examples of factors that might increase the risk for having ASD. Beyond these factors, certain people are at higher risk than others. For example, ASD is four times more common in males than females.
Rates of autism are highest in kids that are born to males over 50 years old. Genetic mutations in sperm rise as men become older, which might add to the risk. Although it's common for women to have children into their forties, they're also the most likely to produce an autistic child.
Prenatal conditions and maternal factors – Problems with a mother's immune system, certain metabolic conditions, or inflammation during pregnancy may be linked with higher autism risk for her children.
Although the exact cause of autism is still unknown, there is evidence to suggest that genetics play a significant role. Since autism is less prevalent in females, autism was always thought to be passed down from the mother. However, research suggests that autism genes are usually inherited from the father.
Siblings with autism share about 66 percent of their genetic material from their father and only about 30 percent from their mother. However, this was a surprising finding with many potential explanations including the complex interaction of parental DNA.
There is not just one cause of ASD. There are many different factors that have been identified that may make a child more likely to have ASD, including environmental, biologic, and genetic factors.
Due to its lower prevalence in females, autism was always thought to have a maternal inheritance component. However, research also suggests that the rarer variants associated with autism are mostly inherited from the father. Ultimately, autism is a complex condition with 100s of genes involved.
This led researchers to investigate the extent to which genetics contribute to the development of autism. Numerous studies, including twin studies and family studies, have estimated the heritability of autism to be around 80 to 90%, indicating that genetic factors play a substantial role in its etiology.
In the United States, prenatal genetic testing (PGT) for Autism Spectrum Disorders (ASD) is currently available via clinical genetic services. Such testing may inform parents about their unborn child's risk for ASD, prepare parents for the birth of an affected infant, and allow them to arrange for early interventions.
If someone in your family has autism spectrum disorder (ASD), you may be more likely to have a child with ASD. ASD can look very different from person to person, so taking a careful family health history can be important for early diagnosis.
We know that there's no one cause of autism. Research suggests that autism develops from a combination of genetic and nongenetic, or environmental, influences. These influences appear to increase the risk that a child will develop autism.
Depression isn't the only mental health factor that can influence pregnancy outcomes. High levels of stress during pregnancy may also be connected to autism in children. This connection appears to have the most impact when the parent experiences stress between weeks 25 and 28 of pregnancy.
A 2022 study found that a routine second-trimester ultrasound could detect early signs of autism during pregnancy,18 including anomalies in the heart, head, and kidneys. These anomalies were found in 30% of fetuses who were later diagnosed with ASD, a three times higher rate than typical fetuses.
In the largest study of its kind, researchers have shown that the risk of autism increases for firstborn children and children of older parents. The risk of a firstborn with an autism spectrum disorder triples after a mother turns 35 and a father reaches 40.
It is estimated that worldwide about 1 in 100 children has autism (1). This estimate represents an average figure, and reported prevalence varies substantially across studies.
Many children show symptoms of autism by 12 months to 18 months of age or earlier. Some early signs of autism include: Problems with eye contact. No response to his or her name.
Doctors look at the child's developmental history and behavior to make a diagnosis. ASD can sometimes be detected at 18 months of age or younger. By age 2, a diagnosis by an experienced professional can be considered reliable. However, many children do not receive a final diagnosis until much older.
One study found that the chance of having ASD for children born to parents who are in their thirties is up to 10 percent higher than parents who are 25 to 29 years old. The same researchers found that the chance of developing ASD is 50 percent higher when the parents are in their 40s or 50s.
Autism susceptibility is currently estimated to be 40–80% genetic.
Men and boys are more frequently diagnosed with autism than women and girls. It is debated whether this is due to a sex difference in rates of autism spectrum disorders (ASD) or whether females are underdiagnosed. The prevalence ratio is often cited as about 4 males for every 1 female diagnosed.
Autism affects about 2% of children with 4:1 male-to-female ratio and a heritability estimate between 70 and 90%. The etiology of ASD involves a complex interplay between inheritance and environmental factors influenced by epigenetics. Over 800 genes and dozens of genetic syndromes are associated with ASD.
For an individual, the risk of autism is increased 10 fold if a full sibling has the diagnosis and about 2 fold if a cousin has the diagnosis. These findings may inform counseling families with affected children.
For starters, a recent study, partly funded by Autism Speaks, found that in families with one or more children with ASD, the chances that a baby sibling will develop autism are much higher than previously thought. In fact, the odds were around one in five, or 20 percent.