Several risk factors present during pregnancy have been associated with autism. Some, like older parental age and use of antidepressants, have strong research support. Others, such as Tylenol (acetaminophen) use and exposure to environmental toxins, need more investigation.

When exploring these, it’s important to remember that an association is not the same thing as a cause. For example, it’s a fact that preterm babies are more likely to have autism than full-term babies, but that doesn’t mean that prematurity causes autism. Furthermore, the connection may have more to do with genetics or socioeconomic factors than birth parent behaviors.

This article discusses the pregnancy-related factors associated with autism, including which ones are supported by the most evidence, which have weaker associations, and what you can do to reduce the risk.

Multiple well-researched, large studies have found a link between certain pregnancy-related factors and autism, and the results have been reproduced in later studies.

These factors, therefore, are valid, though they raise the risk of autism only slightly. If it’s possible for you to minimize these risks, your likelihood of having a child with autism will be reduced.

Use of Antiepileptic Drugs

Some common antiepileptic drugs, particularly valproate (sold under the brand name Depakote), have been shown to increase the risk of autism when taken by the childbearing parent during pregnancy. Valproate, in particular, may raise the risk by as much as 10%.

If you are considering pregnancy, talk with your neurologist about changing or even stopping your medication to reduce the risk of autism.

Use of Antidepressants

The use of antidepressants, particularly selective serotonin reuptake inhibitors (SSRIs), are also linked to autism risk.

The findings of a 2015 systematic review and meta-analysis support an increased risk of autism in children of mothers exposed to SSRIs during pregnancy.

Older Parental Age

Quite a few large studies suggest that older parents are significantly more likely to have children with autism.

There is some evidence to suggest that this phenomenon is more likely when the male genetic parent is older, though there is some evidence that the age of the childbearing parent is a factor, as well.

Preterm Birth

A number of studies have found an association between preterm birth and autism, as well as other developmental disorders. About 7% of children born preterm have autism, compared with 1%–2% of children in the general population.

Low birth weight is a related risk. While there is no way to completely eliminate the risk of early delivery, it is possible to lower that risk.

Speak with your doctor if you are at increased risk of delivering early.

Gestational Diabetes

A large 2021 review showed that if the birth parent experiences gestational diabetes (diabetes first diagnosed when pregnant), there is a greater-than-average likelihood of having a child with autism. This type of diabetes is also associated with preterm birth, preeclampsia, and attention deficit hyperactivity disorder (ADHD).

Any form of diabetes mellitus in the birth parent can be a risk factor.

Gestational diabetes can’t always be avoided, but it can be carefully managed with the support of a doctor. Maintaining healthy blood sugar levels during your pregnancy may minimize the impact the condition could have on fetal development.

Some risk factors have been researched by well-established individuals under appropriate circumstances, but the findings have not been reproduced enough times to be conclusive.

If you have concerns, you’re better off avoiding these possible risks, though it’s not absolutely certain that they will increase your risk of having a child on the autism spectrum.

Taking Tylenol (Acetaminophen) During Pregnancy

Use of Tylenol during pregnancy is very common as it is one of the only pain relievers considered safe during pregnancy. However, there is a growing concern that it may be linked to increased risks to a fetus, including for neurodevelopmental disorders such as autism and attention deficit hyperactivity disorder (ADHD).

Birth cohort studies in Spain and Denmark found an association between Tylenol use during pregnancy and autism in children. One smaller study of the umbilical cord blood of children who were later diagnosed with autism or ADHD found that those with more acetaminophen in their pre-birth blood supply were more likely to develop the disorders.

The American College of Obstetricians and Gynecologists (ACOG) does not recommend any changes in how physicians prescribe acetaminophen until more definitive research is done.

Iron Deficiency

Iron is important for fetal brain development. However, iron deficiency is common during pregnancy; nearly half of pregnant persons not getting enough iron.

A 2014 study published in American Journal of Epidemiology found an association between maternal iron deficiency and an increased risk of autism. This risk was found to be much greater with higher maternal age and the presence of metabolic conditions during pregnancy.

Environmental Toxins

Exposure to certain toxins found in some plastic goods, newly built houses, new carpets, and even some food packaging may increase the risk of autism. While earlier studies found a connection, more recent studies were inconclusive.

Such toxins include:

  • Bisphenol A (BPA)Polybrominated diphenyl ethers (PBDEs)Polychlorinated biphenyls (PCBs)Polychlorinated dibenzodioxins (PCDDs)

Other environmental exposures that have been linked to autism include:

  • Traffic-related air pollutantsCertain heavy metalsSeveral pesticides

Health Issues

According to several meta-analyses (analyses of multiple studies on the topic), the following pregnancy-related issues are associated with autism in more than one study:

  • Autoimmune disease in the birth parent Infections during pregnancy Prenatal stress

A single, older meta-analysis uncovered a much longer list of possible pregnancy issues associated with increased risk of autism, including:

  • Abnormal presentation of the fetusUmbilical cord complicationsFetal distressBirth injury or traumaMultiple births (twins, triplets, etc.)Maternal hemorrhageLow birth weightSmall for gestational ageCongenital malformationFeeding difficulties

While this list is long, it’s important to remember that many of these issues may appear in a single pregnancy and birth, and are usually associated with premature birth. For example, prenatal stress, congenital malformation, and other issues may lead to an early birth, which is associated with low birth weight.

Premature infants often have issues with feeding. A baby who has low birth weight but is born at full-term and has no other issues may have only a tiny statistically increased risk of autism.

Reducing Risk of Autism During Pregnancy and Birth

Based on the research, there are several steps a birth parent can take to reduce the risk that their child will have autism. They include:

Can I Find Out if My Unborn Baby Will Have Autism?

While the early signs of autism typically appear in the first one to two years of life, emerging research suggests there may be signs of autism during pregnancy. A 2022 study, which examined brain MRI scans of fetuses who were later diagnosed with autism, found certain regions (insula and amygdala) were enlarged. The researchers suggested that such findings during pregnancy may be able to predict the emergence of autism later in life.

  • Having children after the age of 21 and before the age of 35 and choosing a male genetic parent in the same age rangeWorking with a doctor to choose safer medications for specific issues, such as epilepsy or depressionAvoiding activities such as smoking and being around known toxinsMaking regular prenatal visits to the doctor and following up on any potential physical issues, such as emerging gestational diabetes   Maintaining a healthy weight during pregnancyClosely following any medical advice regarding bed rest and stress avoidance

According to studies, a fetus may also benefit from consistent and appropriate use of specific supplements.

Research findings mention taking supplements such as folate (folic acid), omega-3s, and vitamin D3, correcting vitamin deficiencies, boosting your immune system, and prolonging breastfeeding as possible ways to reduce the risk of autism (though, of course, they can’t eliminate the risk altogether).

Summary

Determining pregnancy-related risk factors for autism is an ongoing area of research. Some risk factors have more evidence of an association than others.

Taking certain antiepileptic drugs, being older parents, having a preterm birth, and developing gestational diabetes are believed to be risk factors. Possible risk factors include environmental toxins and taking Tylenol during pregnancy.

A Word From Verywell

Every pregnancy is unique, and it is impossible to avoid all potential risks to your baby. Simple measures can, however, decrease risks for many conditions.

At the same time, it’s important to remember that autism is known to have a strong connection to genetics. If you or your partner has autism or you have family members on the spectrum, your risk of having a child with autism increases no matter how carefully you manage your pregnancy.