Avoiding Environmental Hazards During Pregnancy

By Alycia Halladay, Ph.D.
Alycia Halladay, Ph.D.

This week’s “Got Questions?” answer is from Autism Speaks Director of Research for Environmental Sciences Alycia Halladay, Ph.D.

I’m pregnant. What can I do to avoid “environmental” risks?

As researchers discover more environmental risk factors for autism, our community justifiably wonders if any are preventable. First it’s important to note that when scientists speak of environmental risk factors, they’re talking about more than exposures to toxic chemicals. By environmental, we’re referring to pretty much any influence beyond inherited genes. Preterm birth with low birth weight, for example, is an “environmental” risk factor for autism spectrum disorder (ASD). Unfortunately, low birth weight often results from unavoidable exposures.

Less clear is the association between autism risk and a mother’s exposure to heavy metals and other potentially toxic chemicals during or even before pregnancy. There is reason to be concerned about high levels of exposure to toxic chemicals in our environment. For this reason, Autism Speaks continues to support research to better understand the effects of chemical exposures during pregnancy. 

We have preliminary evidence that pesticides may increase risk of autism. But we cannot, at this time, say that avoiding exposure of pesticides – or any particular chemical – will reduce autism risk in a child or future child.

What we can say is that exposure to toxic chemicals during pregnancy or early infancy poses a general threat to future health. High lead exposure has been shown to lower IQ scores. Certain endocrine disrupting chemicals have been linked to birth defects. So it’s reasonable for parents to take reasonable steps to avoid these exposures.

For guidance the American Journal of Obstetrics and Gynecology recently published two important articles: “Toxic environmental chemicals: the role of reproductive health professionals in preventing harmful exposures" and “Environmental Exposures: How to Counsel Preconception and Prenatal Patients in the Clinical Setting." Both provide specific recommendations on how physicians can advise women who are pregnant or planning to become so. They discuss chemical hazards in ways that empower women to make decisions about their daily living routines and diet. Below is a list of the toxins mentioned in the article with recommendations on how to minimize exposure before conception and during pregnancy and breast feeding. 

We want to emphasize that, we cannot say whether reducing exposure to these chemicals will lower the risk of autism in a future child. However, we do know that avoiding exposure to these particular chemicals may improve the overall outcome of the child throughout the entire life.

Toxic chemicals to avoid during pregnancy


  • Exposure can come from eating fish, contact with quicksilver and use of certain skin-lightening creams. Exposure during pregnancy can lead to adverse neurodevelopmental outcomes that include lower IQ, poor language and impaired motor development.
  • To reduce exposure, pregnant women should avoid direct exposure and follow U.S. Environmental Protection Agency and state-specific fish consumption guidelines. In particular, avoid shark, swordfish, king mackerel, tile fish and large tuna


  • Risk factors for high exposure include recent immigration to the United States, occupational contact, imported cosmetics and renovation of homes built before 1978.
  • To reduce exposure, avoid eating nonfood items (clay, soil, and pottery or paint chips) and jobs or hobbies that may involve lead exposure – including the repair, repainting and renovation work in homes built before 1978. Avoid cosmetics, food additives and medicines imported from overseas. Remove shoes at the door to prevent tracking in lead and other pollutants. 


  • Exposure can result from eating pesticide-contaminated produce and using pesticides in the home and garden, including on pets. Exposure to pesticides in pregnancy has been shown to increase risk of poor prenatal growth, birth defects, leukemia and impaired neurodevelopment.
  • To reduce exposure, avoid using chemical tick and flea collars or dips and other pesticides, both indoors and out. Wash produce thoroughly before eating. Remove shoes at the door to prevent tracking lawn chemicals and other pollutants. For information on the Environmental Working Group’s “Dirty Dozen” (most contaminated food products), click here

Endocrine-disrupting chemicals

  • Endocrine-disrupting chemicals include bisphenol A (BPA) and phthalates, which are commonly found in household objects and in food containers. These chemicals can mimic or block the effects of naturally occurring hormones in the body. In some cases, the adverse health effects can be passed on to future generations. Prenatal exposure to phthalates is associated with changes in male reproductive anatomy and behavioral changes in young girls. Animal studies suggest prenatal exposure to BPA is associated with obesity, reproductive abnormalities and neurodevelopmental abnormalities in offspring.
  • To reduce exposure, decrease consumption of processed and canned foods. Avoid the food-or drink-related use of plastics with recycling codes #3, #4 and #7. When removing old carpet padding, use a vacuum fitted with a HEPA filter to avoid exposure to contaminated dust. For more information, see the advisories at the following government websites: NIH, CDC and EPA.

Thanks to donor support, Autism Speaks continues to fund research into autism’s environmental risk factors.