Scientists reviewed research about autism spectrum disorder (ASD) to understand what causes it. They found that several things happening during pregnancy might increase the chance a child develops autism, including the mother’s immune system being activated by infections, exposure to harmful chemicals, the mother having autoimmune diseases, and problems with how the baby’s brain uses folate (a B vitamin). The study shows that autism isn’t just about genes—what happens in the environment before and after birth also matters. This knowledge could help doctors identify which babies might be at higher risk and develop ways to prevent or reduce autism symptoms.

The Quick Take

  • What they studied: How things that happen during pregnancy—like infections, pollution, the mother’s immune system problems, and vitamin deficiencies—might contribute to autism development in children
  • Who participated: This was a review of many existing studies, not a single study with participants. Scientists looked at hundreds of research papers to find patterns and connections
  • Key finding: Four main pregnancy factors appear to work together to increase autism risk: maternal immune activation (when the mother’s immune system reacts strongly), environmental toxins (poisons in the air or water), autoimmune diseases in the mother, and problems with folate processing in the baby’s brain
  • What it means for you: If you’re pregnant or planning to become pregnant, this research suggests that managing infections, reducing exposure to pollution, treating autoimmune conditions, and ensuring adequate folate intake may be important. However, this is not medical advice—talk to your doctor about your specific situation

The Research Details

This is a review article, which means scientists read and analyzed many other research studies to find common themes and patterns. Instead of doing their own experiment with participants, the researchers looked at what other scientists had discovered about autism and pregnancy. They focused on four specific areas: how the mother’s immune system responds during pregnancy, exposure to environmental toxins like pesticides and air pollution, autoimmune diseases (where the body attacks itself), and problems with folate metabolism (how the body uses this important B vitamin). By combining findings from many studies, they could see how these factors might work together to affect brain development.

This type of review is valuable because it helps scientists and doctors understand the bigger picture. Rather than looking at one small study, they can see patterns across many studies done by different researchers in different places. This makes the conclusions stronger and more reliable. The researchers were careful to look at the actual biological mechanisms—the specific ways these factors might change how the brain develops—not just whether they’re connected.

Understanding how autism develops is crucial for prevention and early treatment. For many years, people thought autism was purely genetic and couldn’t be changed. This review shows that’s not the whole story. By identifying environmental and immune factors that contribute to autism, doctors might be able to reduce risk during pregnancy and early childhood. This could mean fewer children developing autism, or developing it less severely. It also helps explain why autism is more common in some families and communities than others—different exposures and health conditions create different risks

This is a review of existing research, not original research, so it’s only as good as the studies it includes. The authors appear to have looked at peer-reviewed scientific papers, which means other experts checked the work before publication. However, review articles can sometimes miss important studies or emphasize certain findings over others. The fact that this was published in a scientific journal suggests it went through quality checks. Readers should know that this summarizes what scientists think based on current evidence, but some of these connections are still being studied and may change as new research comes out

What the Results Show

The research identifies four main pathways that may increase autism risk during pregnancy. First, when a pregnant woman’s immune system becomes very active—such as during a serious infection—it may affect how the baby’s brain develops. Second, exposure to environmental toxins like pesticides, heavy metals, and air pollution may harm developing brain cells. Third, when a mother has an autoimmune disease (where her immune system attacks her own body), this can increase autism risk in her child. Fourth, some children may have problems using folate in their brains, even if they get enough of this vitamin, because their bodies make antibodies (immune proteins) that block folate from working properly.

These four factors don’t work in isolation. Instead, they appear to interact with each other and with a child’s genes. A child with genetic vulnerability to autism who is also exposed to multiple environmental stressors during pregnancy may have higher risk than a child with the same genes but fewer exposures. This explains why autism is complex—it’s not caused by just one thing, but by a combination of factors.

The research suggests that the timing of these exposures matters significantly. Certain periods during pregnancy appear to be more sensitive to these influences than others. Disruptions during critical windows of brain development may have bigger effects than disruptions at other times. This is why understanding when exposures happen is just as important as understanding what the exposures are.

The review also discusses how these factors might trigger or worsen autism symptoms after birth. Environmental infections and pollution can continue to activate the immune system even after pregnancy ends. In children with autoimmune conditions or folate metabolism problems, these postnatal triggers may have stronger effects. The research suggests that some children may be particularly vulnerable to these triggers because of what happened during pregnancy, creating a lasting sensitivity. Additionally, the findings suggest that identifying these risk factors early could allow doctors to monitor children more closely and potentially intervene before symptoms become severe

This research builds on decades of studies showing that autism has both genetic and environmental causes. Earlier research focused mainly on genes, but over the past 15-20 years, scientists have increasingly recognized that environmental factors matter too. This review brings together that newer research and shows how different environmental factors might work together. It also connects autism research to broader understanding of how the immune system affects brain development, which has been studied in other conditions. The emphasis on folate metabolism is relatively newer in autism research, though folate’s importance in pregnancy has been known for decades

This is a review of other studies, not original research, so it depends on the quality of those studies. Some of the connections described are still being studied, and not all scientists agree on how strong these connections are. The review focuses on biological mechanisms but doesn’t provide clear numbers about how much each factor increases autism risk. Additionally, most research on these topics has been done in developed countries, so the findings may not apply equally to all populations worldwide. The review also cannot prove that these factors cause autism—it shows associations and possible mechanisms, but proving cause and effect requires different types of studies. Finally, individual cases of autism are complex, and this general framework may not explain every child’s situation

The Bottom Line

For pregnant women or those planning pregnancy: (1) Work with your doctor to manage infections promptly, as severe infections may increase risk. (2) Reduce exposure to environmental toxins by avoiding pesticides when possible, minimizing air pollution exposure, and being cautious with chemicals. (3) If you have an autoimmune disease, ensure it’s well-managed during pregnancy with your doctor’s guidance. (4) Ensure adequate folate intake through diet (leafy greens, legumes) or supplements as recommended by your doctor. (5) Maintain overall health through good nutrition, exercise, and stress management. Confidence level: Moderate. These are evidence-based suggestions, but they’re not guaranteed to prevent autism, as genetics and other unknown factors also play roles

This research is most relevant for pregnant women, women planning pregnancy, and their healthcare providers. It’s also important for parents of children with autism who want to understand what may have contributed to their child’s condition. Public health officials and policymakers should care about this research because it suggests that reducing environmental toxins and improving access to prenatal care could benefit public health. However, this research should not be used to blame parents—autism develops through complex interactions that are often beyond anyone’s control. People without plans to become pregnant can still benefit from understanding this research because it highlights the importance of environmental health for everyone

If these factors are addressed during pregnancy, any protective effects would likely appear in the child’s development over the first few years of life. Changes in brain development happen gradually, so differences might not be obvious immediately after birth but could become apparent as the child grows. If interventions are started after a child is born, benefits might take months to years to become noticeable. It’s important to have realistic expectations—these changes may reduce risk or severity but cannot guarantee prevention of autism

Want to Apply This Research?

  • For pregnant users: Track weekly exposure to potential toxins (pesticide use, air quality index in your area), immune system events (infections, fever), autoimmune disease flare-ups, and folate intake through diet and supplements. Rate each on a simple scale to identify patterns over time
  • Users can set reminders to: (1) Take folate supplements as recommended by their doctor, (2) Check daily air quality and plan outdoor activities accordingly, (3) Log any infections or immune-related symptoms, (4) Track autoimmune disease management activities, (5) Record dietary sources of folate. Create a simple dashboard showing these factors over weeks and months
  • Establish a baseline of current exposures and health status, then track changes month-to-month. Share reports with healthcare providers during prenatal visits. Use the app to identify which factors are most controllable in your specific situation and focus efforts there. Set goals for reducing modifiable risk factors while working with your doctor on medical management of autoimmune conditions or infections

This article summarizes scientific research about factors that may be associated with autism development. It is not medical advice and should not replace consultation with qualified healthcare providers. Autism is a complex condition with multiple causes, and this research does not prove that any single factor causes autism or that preventing these exposures will prevent autism. If you are pregnant, planning pregnancy, or have concerns about autism risk, please discuss this research with your doctor or a genetic counselor who can provide personalized guidance based on your individual circumstances. This information is for educational purposes only.