Healthy diet during pregnancy lowers childhood autism risk

By Dr. Liji Thomas, MDReviewed by Benedette Cuffari, M.Sc.Jul 23 2024

A new prospective study published in JAMA Network Open investigates the impact of pregnancy eating habits on the risk of childhood autism.

Study: Healthy Prenatal Dietary Pattern and Offspring Autism. Image Credit: Pixel-Shot / Shutterstock.com

The prenatal diet and fetal health

About 1-2% of the general population is diagnosed with autism spectrum disorder (ASD), which is primarily characterized by difficulties in social communication, as well as restricted, repetitive behavior and interests. These symptoms may be present together or alone.

Dietary patterns during pregnancy significantly impact the growing fetus. Nevertheless, the role of dietary habits during pregnancy on the risk of autism has not been evaluated, with most studies focusing on one or more specific nutrients or foods such as vitamin D, multivitamins, folic acid, or fish intake. Importantly, the interactions of nutritional components often have synergistic or detrimental effects on health outcomes.  

About the study

The current study obtained data from the Norwegian Mother, Father, and Child Cohort Study (MoBa) and Avon Longitudinal Study of Parents and Children (ALSPAC) conducted in Norway and Southwest England, respectively. Study participants were recruited between 2002-2008 and 1990-1992 for the MoBa and ALSPAC cohorts, respectively, which comprised 84,548 and 11,760 pregnant women, respectively.

All study participants had singleton pregnancies, and their food habits were assessed using food frequency questionnaires. The children born to these mothers were monitored until they were at least eight years old.

The assessed outcomes for the MoBa cohort included a diagnosis of autism, impaired social communication, and restrictive and repetitive behaviors at three years of age. Only social communication difficulties at eight years of age were assessed for the ALSPAC cohort.

The MoBa study utilized the Social Communication Questionnaire (SCQ) for autism-associated social communication difficulties (SCQ-SOC) and restrictive and repetitive behaviors (SCQ-RRB). For ALSPAC, the Social and Communication Disorders Checklist (SCDC), which measures social and communication skills, was used.

Mothers were stratified according to their adherence to a healthy diet pattern into low, medium, and high adherence groups. A healthy prenatal dietary pattern (HPDP) was defined as one that includes fruits, vegetables, nuts, whole grains, and fish. Lower adherence to HPDP was identified when foods with higher fat and refined sugar content were reported.

What did the study show?

Mothers with high adherence to a healthy diet had children who were at a reduced risk of autism as compared to those with low adherence. Overall, mothers who followed a healthy diet during pregnancy had a higher mean level of education, were older, more likely to be nonsmokers, and used prenatal vitamins during pregnancy.

In the MoBa cohort, follow-up at three years showed a 24% reduction in the risk of social communication difficulties among children born to the high adherence cohort compared to those born to the lowest adherence cohort. For the ALSPAC cohort, follow-up at eight years showed a similar reduction in risk.

Females had a higher reduction in risk than males. Notably, girls often develop communication skills earlier than boys, which may contribute to this observation.

Autism-associated behavioral traits were not significantly associated with maternal dietary habits during pregnancy. This observation may be due to several reasons; for example, communication difficulties or repetitive behaviors may be detected in children who do not have autism, especially in younger children.

Both SCQ and SCDC screen for autism; however, only SCDC measures social communication skills. Moreover, at three years of age, the SCQ-RRB cannot distinguish between autism and non-autistic conditions; however, the SCQ-SOC can.

We estimated that only approximately one-fifth of children with a high SCQ score at age 3 years continued to score highly at age 8 year.”

Conclusions

The risk of having a child diagnosed with autism or who exhibits difficulties with social communication was lower among mothers who consumed a healthy prenatal diet. Nevertheless, repetitive and restrictive behavioral traits, despite being associated with autism, failed to show similar associations.

The study findings extend previous research with conflicting results. The current study's use of different scales also allows researchers to identify potential sources of these various observations, such as the age at assessment or subdomains used.

The current study provides important insights into the relationship between a prenatal diet and autism risk that should be explored mechanistically and validated in future research. Alternative methods and tools should also be used to examine these associations.