“Firstborn offspring of two older parents,” Durkin's study noted, “were three times more likely to develop autism than were third- or later-born offspring of mothers aged twenty to thirty-four and fathers aged under forty years.”
It's possible that pregnant women who already have one child may catch infections from their firstborns, resulting in inflammation. Increased inflammation early in pregnancy is associated with autism risk.
Having one child with autism raises the odds of having a second child with the disorder 20-fold, according to one of the largest epidemiological studies so far to address the inheritance of autism risk1.
Children born to older parents are at a higher risk for having autism. Parents who have a child with ASD have a 2 to 18 percent chance of having a second child who is also affected. Studies have shown that among identical twins, if one child has autism, the other will be affected about 36 to 95 percent of the time.
Does The Father Or Mother Carry The Autism Gene? Autism was always thought to have a maternal inheritance component, however, research suggests that the rarer variants associated with the disorder are usually inherited from the father.
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.
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.
Advanced parental age at time of conception. Prenatal exposure to air pollution or certain pesticides. Maternal obesity, diabetes, or immune system disorders. Extreme prematurity or very low birth weight.
Genetics. Several different genes appear to be involved in autism spectrum disorder. For some children, autism spectrum disorder can be associated with a genetic disorder, such as Rett syndrome or fragile X syndrome. For other children, genetic changes (mutations) may increase the risk of autism spectrum disorder.
One is paternal age – older fathers have been linked with higher autism risk. Siblings also play a role. Research from the University of California, Davis (UCD) found that children with at least one older sibling with ASD have an 18 percent chance of also having the disorder.
Scientists theorize that may because they share the same prenatal environment. Identical twins, who have the same genes, have the highest rate of both having autism – 88 percent – among all siblings.
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.
Children who have an older sister with autism are more likely to also have the condition than are those who have an older brother on the spectrum. The risk is higher among younger brothers than younger sisters.
The results of studies vary from 5 to 400 percent. One 2017 study based on whole-genome sequencing of nearly 5,000 people suggests that parents in their mid-40s are 5 to 10 percent more likely to have a child with autism than are 20-year-old parents.
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.
Autism Can Start During Second Trimester of Pregnancy.
The behavioral symptoms of autism spectrum disorder (ASD) often appear early in development. Many children show symptoms of autism by 12 months to 18 months of age or earlier.
Genetics. Genetic factors may be the most significant cause of autism. Early studies of twins had estimated heritability to be over 90%, meaning that genetics explains over 90% of whether a child will develop autism.
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.
Rather than including all children in a given region, some research focuses only on children with ASD and their siblings. Studies that include all siblings born before and after the child who has ASD have found the ASD recurrence risk to be 6-10% (Bolton et al., 1994; Chudley, Guitierrez, Jocelyn, & Chodirker.
Are all birth defects discovered before a baby is born? It's not always possible to detect all birth defects in utero. However, high-resolution ultrasounds done by certified prenatal ultrasound groups make it possible to diagnose defects that will cause a significant impact before birth.
1 in 100 children are diagnosed with autism spectrum disorder as of 2021. Autism prevalence has increased 178% since 2000. The country with the highest rate of diagnosed autism in the world is Qatar, and the country with the lowest rate is France.
Researchers speculate that exposure to high blood sugar during pregnancy may affect a fetus's brain development and heighten the risk for developmental disorders. A 2021 study also showed a possible connection between high blood sugar during pregnancy and autism risk.