7 Risk Factors for Autism

Medically Reviewed By William C. Lloyd III, MD, FACS
Written By Mary Elizabeth Dallas on September 3, 2020
  • Autism
    Shedding Light on Autism
    Doctors don’t know what causes autism spectrum disorder (ASD). It doesn’t appear to have one single cause. Instead, it’s likely many things come together to increase a child’s risk for this range of disorders. Some risk factors may be genetic — a child inherits them. A child’s environment might also play a role, even before he or she is born. Here's what you need to know about risk factors for ASD.
  • Multigenerational Hispanic family on porch
    Family History
    Autism tends to run in families. Children who have a sister or brother with ASD are at greater risk for having autism. Parents who have a child with ASD are more likely to have another child with the condition. Relatives of a child with autism are also at greater risk for mild problems with communication or social skills.
  • Nurse and premature baby
    Premature Birth
    ASD may develop around the time a child is born — before, during or right after delivery. Problems during pregnancy may cause babies to be born too soon. Research suggests these problems may be linked to ASD. Babies born very early — before 26 weeks of pregnancy — may have an even greater risk for developing one of these disorders.
  • 3D DNA
    Genetics may play a role in why some people develop ASD and others don't. Research involving identical twins shows when one twin is affected, the other twin will have ASD 36 to 95% of the time. In addition, certain genetic conditions are linked to autism. About 10% of children with ASD also have a genetic or chromosomal disorder. These include Down syndrome, fragile X syndrome, Tourette syndrome, and tuberous sclerosis. Random gene changes called mutations can also increase the risk of autism.
  • Pest control technician using high pressure spray gun with heavy duty gloves on shrubbery
    Exposure to certain chemicals before birth may increase a baby's risk for ASD. Pregnant women who take certain medications may be more likely to have a child with one of these disorders. These medicines include drugs to control mood (thalidomide), manage seizures (valproic acid), or stop premature labor (terbutaline). Unborn babies exposed to pesticides and chemicals often found in plastics (phthalates) might also have an increased risk of ASD.
  • Grand mother with baby
    Parents' Age
    The age of the parents seems to affect a child's risk of ASD. For instance, autism rates are higher among children born to dads older than 50. Genetic mutations in sperm increase as men age. This may help explain the higher risk. Also, women in their forties are slightly more likely to have a child with ASD. But, babies born to teen moms are also at increased risk. Doctors don’t know why a mom's age affects her child’s risk for ASD. Autism is also more common among couples with a gap in their ages of 10 or more years.
  • Mixed race mother admiring newborn baby son
    Being Male
    ASD affects people of all races, ethnicities and backgrounds. Health officials estimate that, today, about 1 in 68 children has one of these disorders. Boys, however, are at much greater risk than girls. ASD is nearly five times more common among boys than girls.
  • Los Angeles
    Pregnant women exposed to high levels of pollution are more likely than other women to have a child with ASD. The risk of autism rises as pollution exposure increases. This link is strongest when exposure occurs in the final few weeks of pregnancy. A baby's genetic makeup can heighten this risk: Autism is more common among children exposed to air pollution before birth who also have a particular version of what's called the MET gene.
  • mother-typing-at-computer-with-child
    What Else You Should Know
    There's a widespread myth that vaccines cause ASD. Some people are concerned about the preservative thimerosal in vaccines that protect against more than one disease. They're particularly worried about the MMR vaccine, which protects against measles, mumps and rubella. However, there is no scientific evidence to support these claims. Vaccines do not cause ASD. Many studies have dispelled this myth. But, scientists still do not know what does cause ASD. It’s an active area of research.
7 Risk Factors for Autism

About The Author

  1. Autism Information. U.S. Department of Health and Human Services. http://www.hhs.gov/programs/topic-sites/autism/index.html
  2. Facts About ASD. Centers for Disease Control and Prevention. http://www.cdc.gov/ncbddd/autism/facts.html
  3. Autism Spectrum Disorder: Risk Factors. Mayo Clinic. http://www.mayoclinic.org/diseases-conditions/autism-spectrum-disorder/basics/risk-factors/con-20021...
  4. Gene Change Plus Prenatal Exposure to Pollution Ups Autism Risk. Autism Speaks. https://www.autismspeaks.org/science/science-news/gene-change-plus-prenatal-exposure-pollution-ups-a...
  5. Autism Spectrum Disorder. National Institute of Mental Health. http://www.nimh.nih.gov/health/publications/autism-spectrum-disorder-qf-15-5511/index.shtml
  6. Avoiding Toxic Exposures During Pregnancy. Autism Speaks. https://www.autismspeaks.org/science/initiatives/environmental-factors-autism-initiative/avoiding-to...
  7. ASD: Data & Statistics. Centers for Disease Control and Prevention. http://www.cdc.gov/ncbddd/autism/data.html
  8. Autism Spectrum Disorder Fact Sheet. National Institute of Neurological Disorders and Stroke. http://www.ninds.nih.gov/disorders/autism/detail_autism.htm#3082_5
  9. Vaccines Do Not Cause Autism. Centers for Disease Control and Prevention. http://www.cdc.gov/vaccinesafety/concerns/autism.html
  10. Large Study on Parent Age & Autism Finds Increased Risk with Teen Moms. Autism Speaks. https://www.autismspeaks.org/science/science-news/large-study-parent-age-autism-finds-increased-risk...
  11. Largest-ever Study on Autism & Pollution Shows Strong Link During Pregnancy. Autism Speaks. https://www.autismspeaks.org/science/science-news/largest-ever-study-autism-pollution-shows-strong-l...
  12. Autism Spectrum Disorder. March of Dimes. http://www.marchofdimes.org/complications/autism-spectrum-disorder.aspx#
  13. Sandin S, Schendel D, Magnusson P, et al. Autism Risk Associated with Parental Age and with Increasing Difference in Age Between the Parents. Molecular Psychiatry. 2016;21, 693–700.
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Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2020 Sep 3
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