A recent study published in the American Journal of Clinical Nutrition highlights the potential benefits of eating fish during pregnancy. Researchers found that maternal fish consumption was associated with about a 20% lower likelihood of an autism spectrum disorder diagnosis in children, particularly in females, and a slight reduction in autism-related traits. However, taking omega-3 supplements, often marketed for similar benefits, did not show the same associations.
Autism spectrum disorder is a neurodevelopmental condition that affects how individuals perceive and interact with the world. It is characterized by challenges in social communication and interaction, along with restricted or repetitive behaviors. Autism exists on a spectrum, meaning its severity and symptoms can vary widely from one individual to another. Some people with autism may require significant support in their daily lives, while others are highly independent and excel in certain areas, such as logic or attention to detail.
The causes of autism are complex and not fully understood. Both genetic and environmental factors are known to play a role. While genetics have a significant influence, researchers are increasingly examining prenatal and early-life environmental exposures to understand their contributions to neurodevelopmental outcomes. Among these factors, maternal nutrition during pregnancy has emerged as a potentially modifiable influence.
Fish is a rich source of omega-3 fatty acids, particularly DHA, which is a key component of brain cell membranes. Previous studies have suggested that fish consumption during pregnancy may support cognitive development and reduce the likelihood of developmental challenges in children. However, concerns about contaminants in fish, such as methylmercury, and the lack of clear evidence linking fish intake to autism outcomes have contributed to uncertainty about its benefits and risks.
“Fish intake is a key source of fatty acids that are important in brain development. Although many studies have examined relationships between eating fish in pregnancy and other child outcomes like IQ scores, few studies have addressed whether eating fish in pregnancy – or not eating enough fish in pregnancy – might relate to autism and related behaviors or traits,” said study author Kristen Lyall, an associate Professor at the AJ Drexel Autism Institute at Drexel University.
The researchers utilized data from the Environmental Influences on Child Health Outcomes (ECHO) Program, a large consortium of studies in the United States examining the impact of early-life environmental factors on child health. The study analyzed data from up to 32 cohorts involving children born between 1999 and 2019, with a total sample size of nearly 4,000 participants for fish intake and over 4,500 for supplement use.
Mothers provided information on their fish consumption during pregnancy using food frequency questionnaires. Fish intake was categorized into four levels: none or less than once a month, more than once a month but less than weekly, weekly, and two or more servings per week. Omega-3 supplement use was also reported, but detailed dose information was not consistently available.
Autism diagnoses were based on parent-reported clinician diagnoses. In addition, autism-related traits were measured using the Social Responsiveness Scale, a standardized tool that assesses social and communication traits associated with autism.
The study found a consistent association between maternal fish consumption and reduced likelihood of autism diagnosis. Any fish consumption during pregnancy was linked to about a 20% reduction in autism risk compared to no fish consumption. Interestingly, this association did not appear to strengthen with higher levels of fish intake; all categories of fish consumption showed similar reductions in risk. The association was particularly pronounced in females, although the results for males also indicated a potential benefit.
For autism-related traits, children of mothers who ate fish during pregnancy had slightly lower scores on the Social Responsiveness Scale, suggesting fewer autism-related traits. However, the reduction was modest—about two points on the scale.
“Our findings are consistent with current dietary guidelines during pregnancy to consume at least 1-2 servings of fish low in mercury per week,” Lyall told PsyPost. “Our results suggested that those who ate fish at least weekly had a lower likelihood of having a child with autism, though it is important to remember that many factors contribute to autism.”
In contrast, omega-3 supplement use was not associated with a reduced likelihood of autism diagnosis or autism-related traits. In fact, there was a small but statistically significant increase in autism-related traits among children of mothers who took supplements. This finding was unexpected and requires further investigation.
“It was somewhat surprising that we saw associations with fish intake, but not with fish oil/omega-3 supplement intake,” Lyall said. “It may be that the biological availability of these critical fatty acids differs in fish vs in supplements, or that other nutrients in fish contribute to the benefits.”
The researchers controlled for factors like maternal age, education, race, and smoking status, as well as the child’s sex and birth year. But there are some limitations to consider. The researchers relied on self-reported data for both fish consumption and autism diagnoses, which may introduce measurement errors. Additionally, the study could not account for differences in fish species or contaminants, such as methylmercury, which may vary in their effects. The data also lacked detailed information on the timing of fish consumption during pregnancy or the dosage of omega-3 supplements.
Future research should explore these factors in more detail, including the specific types of fish consumed, the role of other nutrients found in fish, and the potential influence of contaminants. Studies that incorporate biomarkers, such as blood levels of omega-3 fatty acids, could provide more precise data. Researchers also emphasized the need to investigate whether the benefits of fish consumption might plateau beyond a certain intake level or vary by trimester.
“We would like to better understand how environmental factors influence neurodevelopment, and provide the best possible information to pregnant persons to guide dietary choices,” Lyall said.
The study, “Association of maternal fish consumption and ω-3 supplement use during pregnancy with child autism-related outcomes: results from a cohort consortium analysis,” was authored by Kristen Lyall, Matt Westlake, Rashelle J. Musci, Kennedy Gachigi, Emily S. Barrett, Theresa M. Bastain, Nicole R. Bush, Claudia Buss, Carlos A. Camargo Jr., Lisa A. Croen, Dana Dabelea, Anne L. Dunlop, Amy J. Elliott, Assiamira Ferrara, Akhgar Ghassabian, James E. Gern, Marion E. Hare, Irva Hertz-Picciotto, Alison E. Hipwell, Christine W. Hockett, Margaret R. Karagas, Claudia Lugo-Candelas, Thomas G. O’Connor, Rebecca J. Schmidt, Joseph B. Stanford, Jennifer K. Straughen, Coral L. Shuster, Robert O. Wright, Rosalind J. Wright, Qi Zhao, and Emily Oken.