If you’re pregnant and searching for what causes autism during pregnancy, or looking back after a diagnosis, wondering whether something during the pregnancy played a role or if you missed any signs of autism during pregnancy, you’re not alone. These are honest, human questions.
This article gives you a clear, evidence-based answer rather than adding to your worry, because the science is more reassuring than most online searches suggest.
Key Takeaways:
- There are no signs of autism during pregnancy, and autism cannot be detected before birth
- No single event, food, feeling, or experience during pregnancy causes autism
- Some prenatal factors are associated with autism in research, but association is not the same as cause
- Vaccines used during childhood and pregnancy do not cause autism
- No parent should blame themselves for a child’s autism diagnosis
- For individual concerns about pregnancy health, speak to your midwife, GP, or prescribing clinician
Disclaimer: This article is for informational purposes only and is not clinical advice. If you have concerns about your pregnancy or your child’s development, please speak to a qualified healthcare professional.
Are There Signs of Autism During Pregnancy?
No. There are no signs of autism during pregnancy, and autism cannot be diagnosed before birth from a pregnant person’s symptoms, an ultrasound scan, or a home test. Autism is identified after birth through developmental assessment, which looks at communication, social interaction, behaviour, sensory experiences, and developmental history.
Searches for “signs of autism during pregnancy” are common and understandable. But the answer is clear: the signs of autism are not visible during pregnancy, and no maternal symptom or scan result can tell you whether a baby will be autistic.
What Causes Autism During Pregnancy?
No single thing causes autism during pregnancy. Autism has a complex genetic and developmental basis, and its origins are not fully understood. Research identifies some prenatal factors associated with a higher likelihood of autism in large groups of people, but that is very different from saying those factors caused autism in any individual child.
The distinction matters. A group-level statistical association does not tell you why your child is autistic. It cannot.
What Does Research Say?
A comprehensive meta-analysis examining over 50 prenatal factors found associations between autism and certain pregnancy complications, including gestational diabetes, advanced parental age, and bleeding during pregnancy.¹ A 2024 review in BMC Medicine identified infection during pregnancy, gestational diabetes, and maternal obesity as established prenatal risk factors, while also noting that the biological pathways behind these associations remain uncertain.²
These findings do not mean that any of these conditions caused an individual child’s autism. They mean that across very large study populations, certain factors appeared more frequently alongside autism diagnoses. That is meaningful for researchers. It does not assign blame to a parent.
Risk Factor, Association, and Cause: What Is the Difference?
This is worth understanding clearly.
A risk factor is something statistically linked with a higher likelihood of an outcome in a group. It does not mean the outcome will happen in any particular person. A statistical association means two things were observed together in research. It does not mean one caused the other. A cause is something shown to directly produce an outcome. No prenatal factor has been shown to directly cause autism.
Most reporting about pregnancy and autism blurs these distinctions. When you read that a certain condition is “linked to” autism, that is an association, not a cause.
Did Stress, Food, or Something I Did Cause Autism?
No. There is no credible evidence that stress, specific foods, lifestyle choices, or ordinary pregnancy experiences cause autism. If you are looking back over your pregnancy trying to find something to blame yourself for, please stop.
The research does not support that kind of individual causal reasoning, and no clinician should encourage it.
Autism is understood to arise through a complex combination of genetic and developmental factors. It is not caused by something a parent did or did not do during pregnancy.
If you are currently pregnant and have specific concerns about a medication, infection, or health condition, speak to your midwife, GP, obstetrician, or prescribing clinician. Do not start or stop any medication based on what you read online.
Do Vaccines During Pregnancy or Childhood Cause Autism?
No. In December 2025, the WHO Global Advisory Committee on Vaccine Safety reviewed 31 primary research studies published between 2010 and 2025, covering data from multiple countries. The committee reaffirmed its previous conclusions from 2002, 2004, and 2012: vaccines, including those containing thiomersal or aluminium, do not cause autism.³ This conclusion applies to vaccines used during both childhood and pregnancy.
The original claim linking the MMR vaccine to autism was based on a fraudulent study. It has been fully retracted. The author lost his medical licence. Every robust investigation since has found no causal link.
What to Do If You Are Worried
If you have personal concerns about pregnancy health, medication, or a specific health condition, your first point of contact should be your maternity team, GP, midwife, or obstetrician. They can give you advice that is specific to your situation. Online articles, including this one, cannot do that.
If your child has received an autism diagnosis and you are processing what that means, the most useful next step is understanding your child’s individual profile and what support is available to them. A formal autism assessment is carried out after birth and considers a person’s development, communication, behaviour, sensory experiences, and current needs. If you are looking for information about the assessment pathway, Autism Detect’s children’s autism assessment explains how the process works and what it involves.
Frequently Asked Questions
Can an ultrasound show autism?
No. Ultrasound scans check physical development and anatomy. They cannot detect autism, which is identified through behavioural and developmental assessment after birth. There are no physical markers visible on a scan that indicate whether a baby will be autistic.
Can stress during pregnancy cause autism?
There is no evidence that ordinary stress during pregnancy causes autism. Some research has examined maternal stress as a prenatal factor, but no study has shown that a parent’s stress directly causes autism in their child. Autism has a complex basis that is not reducible to a single prenatal experience.
Can medication during pregnancy cause autism?
Some research has examined associations between certain medications taken during pregnancy and autism diagnoses in children. These are statistical associations, not proof that a specific medication caused autism in any individual child. If you have concerns about medication you are taking or have taken during pregnancy, speak to your GP, obstetrician, or prescribing clinician. Do not stop prescribed medication without medical advice.
When can autism first be identified after birth?
Signs of autism can sometimes be noticed in the first two years of life, though many autistic people are not identified until later childhood or adulthood. Autism is identified through developmental assessment, not through any single test or scan. A formal diagnostic assessment considers developmental history, communication, social interaction, behaviour, and sensory experiences.
References
[1] Gardener, H., Spiegelman, D. and Buka, S.L. (2009) Prenatal risk factors for autism: comprehensive meta-analysis. The British Journal of Psychiatry, 195(1), pp. 7–14. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3712619/
[2] Love, C., Sominsky, L., O’Hely, M., Berk, M., Vuillermin, P. and Dawson, S.L. (2024) Prenatal environmental risk factors for autism spectrum disorder and their potential mechanisms. BMC Medicine, 22, Article 393. https://pmc.ncbi.nlm.nih.gov/articles/PMC11404034/
[3] World Health Organisation Global Advisory Committee on Vaccine Safety (2025) WHO expert group’s new analysis reaffirms there is no link between vaccines and autism. Available at: https://www.who.int/news/item/11-12-2025-who-expert-group-s-new-analysis-reaffirms-there-is-no-link-between-vaccines-and-autism [Accessed: July 2026].
