Ongoing research is revealing more about factors, like low birth weight, that may determine whether your child will be born autistic. You may be able to influence some of these variables.

Autism spectrum disorder (ASD) is a neurodevelopmental difference that affects each person in a unique way. Many autistic people live independent and fulfilling lives. They don’t feel they need treatment or that their autism should have been prevented.

Other autistic people live with support and limitations to their independence. You might be thinking about these people if you’re pregnant and wondering how to prevent autism.

While factors like family history aren’t something you can change, there may be other steps you can take to reduce the chance of autism in your child.

There isn’t a lone cause of autism. Instead, researchers believe a combination of genes and environment can lead to this neurodevelopmental difference.

It may be possible to modify the effects of some of these factors.

Parent age

Waiting to have children may increase the chance your baby will be autistic. A large 2015 study found that advancing maternal and paternal age was associated with an increased likelihood of having an autistic child.

The age effect may also extend to grandparents. A 2020 study indicates an association between autistic children and the ages of their grandparents when their parents were born.

The findings suggest that the chance of autism increases if the parents were born to grandparents older or younger than 25 to 29 years of age.

Low birth weight and preterm birth

Low birth weight may increase the chance that your baby is autistic. A 2016 study of preterm births examined several factors contributing to ASD and intellectual disability (ID).

It’s important to remember that ASD and ID are distinct cognitive profiles that can occur together or separately. Autistic people can have any intellectual level, ranging from ID to giftedness.

The study found that fetal growth restriction was associated with autism without intellectual disability.

It also found connections between:

  • preterm birth and ASD, with or without ID
  • cervical-vaginal infection and ASD with ID
  • fever in the mother, before, during, or immediately following birth, and ID without ASD

Family history

Having other ASD family members increases the chance your child may be born autistic. The heritability of autism is estimated to be about 64% to 91%, and researchers have identified over 200 genes related to autism.

A family history of other neurological conditions may also increase the odds. According to a 2019 study, the occurrence of autism was linked to family histories that included:

You can’t control your family history. But knowing how it affects your baby’s chance of being autistic can prepare you to spot the early signs and access support.

Children identified at younger ages can benefit from skill-building therapies and public school accommodations if needed.

Exposure to contaminants during pregnancy

Exposure to contaminants like certain pesticides or air pollution while pregnant may increase the chance that your child may be born autistic. The contaminants themselves don’t cause autism but instead trigger changes in genetically inclined babies.

A 2022 study found a link between autism diagnoses and pollution exposure during pregnancy. The study examined exposures to particulate matter, nitrogen dioxide, and ozone.

Researchers found no association between autism and nitrogen dioxide and mixed results for ozone. But the study data indicated an association between autism and exposure to particulate matter pollution in the first two trimesters of pregnancy.

There are steps you can take to reduce your exposure to particulate matter pollution during pregnancy:

  • use a home air purifier
  • grow air purifying plants
  • use a range hood fan while cooking
  • monitor the Air Quality Index (AQI) for your location
  • stay indoors when the AQI readings aren’t green


If your immune system is dysregulated while you’re pregnant, there’s a chance your baby could be born with ASD.

When maternal autoimmunity is present, antibodies can cross the placenta, where they may interfere with the development of the fetus. It may be possible to use certain maternal autoantibodies as diagnostic markers, according to the authors of a 2018 study.

If you live with an autoimmune disease, your doctor may recommend that you achieve remission for several months before attempting pregnancy.

Other care strategies include:

  • regular monitoring of the fetus
  • reviewing your medication regimen
  • exercise
  • dietary supplements
  • caffeine limits
  • smoking cessation

Extra weight gain during pregnancy

Avoiding too much extra weight while pregnant is a factor you might be able to control.

According to a 2020 abstract, excess gestational weight gain (GWG) may contribute to autism in offspring.

The study found that low GWG didn’t have the same effect, and the prepregnancy BMI of the mothers didn’t seem to influence outcomes. It was only the weight gained during pregnancy that made the difference.

The old saying “eating for two” may prompt you to eat more than 300 extra calories per day required during pregnancy.

Instead, you can try:

  • avoiding oversized portions
  • eating fruits, vegetables, and whole grains
  • hydrating with water rather than sugary drinks
  • choosing reduced-fat dairy
  • discussing pregnancy-safe exercise options with your doctor

Assessing the chance of autism for your unborn child may be possible.

According to a 2015 study, prenatal genetic testing (PGT) is available in the US through clinical genetic services. This test looks for ASD susceptibility genes and measures ASD risk only. Babies with these genes may or may not develop autism.

A doctor specializing in maternal-fetal medicine, such as an obstetrician/gynecologist, performs fetal genetic testing using amniocentesis between 16 to 20 weeks gestation.

Placenta shape may also be an identifying factor, as indicated in a 2018 study of unborn younger siblings of autistic children. The ASD siblings had slightly thicker placentas that were rounder with more regular perimeters than placentas measured from the general population.

A placenta’s shape variation is thought to result from its ongoing growth adaptations in response to the changing intrauterine conditions. If a placenta is uniform in shape, this may indicate that it hasn’t been able to compensate for changes in the uterus as well as it should.

A trained technician can examine your placenta using an ultrasound. This safe and noninvasive technology uses sound waves to generate a computer image that the tech can measure.

Autism is a neurodevelopmental difference that has both genetic and environmental causes.

You may be able to influence some factors that contribute to autism, such as your exposure to particulate matter pollution while you’re pregnant.

There are other aspects over which you have no control, like your family history. Still, it helps to have the information you need to prepare for the possibility that your child could be born autistic.

If you’re interested in finding out more about autism funding, support, and information, the US Department of Health and Human Services has an agencies and organizations page you can visit.