Can You Prevent Autism in Pregnancy?

What causes autism during pregnancy? And is there anything you can do during pregnancy to reduce the risk?

Autism spectrum disorder (ASD) is a developmental disability caused by differences in how the brain processes information. As a result, autistic people may behave, communicate, and learn differently from people without ASD.

There is no cure for autism, and experts still do not fully understand why some people develop it. However, research suggests that environmental exposures, including those that occur during conception and pregnancy, may increase the risk of autism in children who are genetically predisposed to the disorder.

Read on to learn the known and potential causes of ASD and whether you can test for autism during pregnancy.

What Is Autism?

Autism is a complex developmental condition that is considered a spectrum because how it affects people can vary significantly from person to person. For example, some autistic people are nonspeaking, while others are not; some need living assistance, while others do not.

ASD is a form of neurodivergence, the idea that some brains function differently. Other forms of neurodivergence include attention-deficit/hyperactivity disorder (ADHD) and dyslexia. Within the framework of neurodiversity, people who are not neurodivergent are sometimes referred to as neurotypical.

The American Medical Association says the strengths of autism include intelligence with computer languages, math systems, and machines; the ability to identify tiny details in complex patterns; and scoring higher on nonverbal intelligence tests. Even so, since society has been constructed to accommodate people who are considered neurotypical, living with ASD can be difficult because autistic people must constantly work to interact in ways neurotypical people expect them to.

Known Risk Factors for Autism During Pregnancy

Experts believe that there are multiple factors (many of which are likely still unknown) that together influence a person's development and potential for autism. That is to say that there is not one known cause of autism, but rather many things that act together to increase the chances of developing the condition.

In discussing risk factors, it's especially important to note that risk factors are not causes; they are factors that increase the chances of someone developing the condition. According to the Centers for Disease Control and Prevention (CDC), available evidence suggests having a sibling with autism, genetic conditions, birth complications, and having older parents are known risk factors for ASD.

Family history

If you already have a biological child with autism, the risk of having another child with ASD increases. A 2019 study found that those with older siblings with childhood autism were 17 times more likely to receive a childhood autism diagnosis themselves. In addition, it found that having a cousin with ASD doubled the chance of an ASD diagnosis, which suggests a strong genetic link.

Genetic conditions

Fragile X syndrome is a genetic condition that causes developmental conditions, including learning disabilities. Research has found it is the most common genetic cause of intellectual disability and ASD.

Another genetic condition linked with autism is tuberous sclerosis complex (TSC). This condition causes tumors in various organs, like the brain, eyes, and lungs. Some research indicates the rate of ASD in children with TSC is as high as 40%.

Birth complications

A 2016 study found a correlation between labor and delivery drugs and ASD. Specifically, it found that children diagnosed with ASD were more than 2.5 times more likely to have been born to gestational parent who had an epidural, Pitocin, or both during their labor and delivery.

The same study also found that children with ASD were more than twice as likely to have experienced a birth complication, including fetal distress, preeclampsia, or breech presentation when they were born.

Older parents

Studies have found that the older a parent is, the greater the chance their child will have autism. This is true for the child's gestational parent and other biological parent.

In a 2016 study of more than 30,000 kids with ASD, researchers found that a maternal age of over 40 and a paternal age of over 50 were associated with an increased risk of ASD. Younger maternal age (under 20) was also associated with a higher risk.

Possible Risk Factors for Autism During Pregnancy

In addition to the established risk factors, there are also some other theories on possible risk factors for autism during pregnancy. While research has found evidence of a connection between these factors and autism, it's unclear whether they are potential causes.

Prenatal vitamin deficiency

A 2020 study evaluated iron deficiency in pregnancy and found that lower iron intakes during were associated with higher autism risks. Low maternal iron is related to neurological development and is associated with other brain development disorders, so it is unlikely to be an independent risk factor for autism, meaning it's unlikely that prenatal iron deficiency alone increases a baby's risk of autism. That said, adequate prenatal iron intake is one simple way to protect your fetus' developing brain.

In addition, a 2022 meta-analysis of 10 studies found that taking folic acid (the synthetic version of folate) in early pregnancy significantly lowers the risk of autism. Taing 400 micrograms (mcg) of folic acid was associated with a reduced risk of autism.

It is recommended that all people who can get pregnant (even those who aren't trying to conceive) should get between 400 to 800 mcg of folate or folic acid daily. Most people get about 150 mcg of daily folic acid from fortified foods such as bread and cereal.

So, check your vitamin's nutrient label, and if necessary, discuss upping your folic acid intake with a health care provider, and add more foods rich in folate (like lentils, spinach, and broccoli) to your diet.

Air pollution

A 2022 study found that exposure to air pollution during all three trimesters of pregnancy increased the risk of ASD, especially in babies assigned male at birth. But, again, researchers see this as a risk factor in susceptible groups rather than an independent risk factor.

"Evidence about environmental risk during pregnancy is really at its infancy, so any data-supported hypotheses must be investigated further as nothing is yet considered a certain cause," says M. Daniele Fallin, Ph.D., director of the Wendy Klag Center for Autism and Developmental Disabilities at the Johns Hopkins Bloomberg School of Public Health. The key is for pregnant people to take safe, proactive steps that can potentially protect their babies.

The American Lung Association recommends several ways to protect yourself from air pollution. For instance, fill your gas tank up after dark, exercise away from highly-trafficked areas, and exercise indoors when pollution levels are high. You can find your area's daily air quality levels with the U.S. Air Quality Index at the Environmental Protection Agency's AirNow website.

Pregnancy weight gain

A 2020 systematic review found that high body mass index (BMI) and excess pregnancy weight gain were related to the risk of ASD in their children. Researchers speculate that hormone dysregulation associated with excess weight gain could affect fetal brain development.

"Obesity rates and autism rates have both gone up over the past decades, yet that doesn't mean the two are connected," says Anna Maria Wilms Floet, M.D., a behavioral developmental pediatrician at the Kennedy Krieger Institute's Center for Autism and Related Disorders in Baltimore.

That said, staying within the recommended weight gain guidelines can help you achieve the best pregnancy outcomes.

Recommended Pregnancy Weight Gain Based on BMI
 Pre-Pregnancy BMI Recommended Pregnancy Weight Gain
 <18.5 28–40 pounds
 18.5-24.9 25–35 pounds
 25-29.9 15–25 pounds
 30+ 11–20 pounds 
Adapted from the Institute of Medicine.

Editor's Note

Body mass index (BMI) is a dated, biased measure that doesn’t account for several factors, such as body composition, ethnic descent, race, gender, and age. Despite being a flawed measure, BMI is widely used today in the medical community because it is an inexpensive and quick method for analyzing potential health status and outcomes.


Gestational diabetes

A 2015 study found that those diagnosed with gestational diabetes by their 26th week of pregnancy were 63% more likely to have a child with autism. That means for every 1,000 people with gestational diabetes, seven of them may have a child with autism.

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. The critical factor may be how high blood sugar levels get.

Interestingly, the 2015 study found that babies born to gestational parents who had type 2 diabetes before getting pregnant didn't have a higher risk of autism, perhaps because they were taking medication to control their blood sugar levels.

Gestational diabetes poses several problems for fetuses, including preterm labor, high birth weight, and an increased risk of obesity and type 2 diabetes later in life. In addition, gestational parents have a higher risk of developing high blood pressure, preeclampsia, and type 2 diabetes.

Medication

Researchers have found potential links between the medication a gestational parent takes while pregnant and a fetus's autism risk. For instance, the class of anti-depressants known as selective serotonin reuptake inhibitors (SSRIs) have shown an association with autism. However, researchers say the results suggest the association is more likely due to maternal depression as a risk factor rather than the drugs that treat it.

In addition, taking anti-seizure medication, including valproate, during pregnancy has been linked with an increased risk of autism. These links highlight the importance of working with a health care provider to determine whether the benefits of the medications you take during pregnancy outweigh the risks. In many cases, they do. For example, the risk of a seizure may pose a much more significant risk to the fetus than a drug that controls seizures.

Child spacing

A study in the Journal of the American Academy of Child & Adolescent Psychiatry found that pregnancies spaced between two and five years apart have the lowest risk of a child developing autism.

Researchers also found that those children conceived less than 12 months after a sibling's birth were 50% more likely to end up with a diagnosis than children conceived between that two-and-five-year time frame, though it's unclear why. Meanwhile, those conceived after more than 60 months were 30% more likely to be diagnosed.

It's important to remember, however, that autism risk increases with both biological parents' ages at conception and that a person's fertility declines as they get older. So, when it comes to timing, work with a health care provider to determine the best plan for you and your family.

Maternal illness

Researchers know that maternal health during pregnancy impacts the fetus, and ASD is no exception to this rule. For instance, those who get very ill with certain infections during pregnancy may be more likely to have children who develop autism. Specifically, studies have shown associations between maternal fever during pregnancy and subsequent risk for their children developing an autism spectrum disorder.

Do your best to remain healthy during pregnancy. Washing your hands frequently, avoiding spending time with people who are ill as much as possible, eating nutritious food, and taking prenatal vitamins are good ways to take care of yourself.

Vaccines Do Not Cause Autism

The myth that vaccines cause autism has been widely disproven. That means that childhood vaccines and those you receive during pregnancy do not increase the risk of ASD.

A large 2020 study found no link between prenatal flu shots and autism in children whose gestational parents received them during pregnancy. The flu vaccine is especially important during pregnancy, as your risk of complications from the flu is greater. Not only that, but receiving the flu vaccine during pregnancy protects your newborn after birth.

The same is true of COVID-19. Pregnant people are at increased risk of complications from infection and prenatal complications, and there is no evidence of maternal or fetal effects from the vaccine. As a result, the American College of Obstetricians and Gynecologists (ACOG) also recommends COVID-19 vaccination during pregnancy.

Can You Test for Autism During Pregnancy?

While autism is typically not diagnosed before the age of 2 (and often much later), it can sometimes be detected earlier. A 2022 study found that a routine second-trimester ultrasound could detect early signs of autism during pregnancy, 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 addition, prenatal genetic testing can sometimes indicate if a fetus is at risk for autism, but these are not widely available in the U.S. For one thing, the tests are not entirely conclusive; for another, they carry moral and ethical dilemmas. For instance, a 2020 study of Taiwanese parents found that 67% of parents would choose prenatal genetic testing for ASD and that more than half would terminate a pregnancy with a risk of ASD.

Some autism advocacy organizations, especially those run by autistic people, feel that autism research focusing on causes or changing genes in utero is harmful because it is seen as a form of eugenics. Instead, many advocates would prefer that research funding goes toward things that help those with autism, such as communication, community living, education, and health care access.

As Autistic Self-Advocacy Network's (ASAN) website says, "Autistic people are an important part of society, and we should get to live our lives as autistic people."

Key Takeaways

While you can't do much to change genetics, you can alter your exposure to certain environmental factors during pregnancy that have shown a link to ASD. However, none of these lifestyle changes are absolutes, and experts can't tell you that lowering your exposure to one particular factor will reduce your child's risk of autism.

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Sources
Parents uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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