A healthy diet during pregnancy reduces a child's risk of developing autism

A recent prospective study published in JAMA Network Open examines the impact of dietary habits during pregnancy on the risk of autism in children.

Approximately 1-2% of the general population is diagnosed with autism spectrum disorder (ASD), which is primarily characterized by difficulties in social communication and restricted and repetitive behaviors and interests. These symptoms may occur together or separately.

Dietary habits during pregnancy have a significant impact on the developing fetus. However, the role of dietary habits during pregnancy on the risk of autism has not been assessed, as most studies have focused on one or a few specific nutrients or foods, such as vitamin D, multivitamins, folate, or fish consumption. It is important to note that interactions between nutrients may have synergistic or detrimental effects on health outcomes.

The present study used data from the Norwegian Mothers, Fathers and Children Cohort (MoBa) and the Avon Longitudinal Study of Parents and Children (ALSPAC), conducted in Norway and South West England, respectively. Study participants were recruited between 2002 and 2008 and 1990 and 1992 for the MoBa and ALSPAC cohorts, respectively, which included 84,548 and 11,760 pregnant women.

All study participants had singleton pregnancies and their dietary habits were assessed using food frequency questionnaires. Children born to these mothers were followed until they were at least eight years old.

For the MoBa cohort, outcomes such as autism diagnosis, social communication impairment, and restrictive and repetitive behavior at age three were assessed. For the ALSPAC cohort, only social communication difficulties at age eight were assessed.

The MoBa study used the Social Communication Questionnaire (SCQ) to assess social communication difficulties (SCQ-SOC) and restrictive and repetitive behaviors (SCQ-RRB). The ALSPAC used the Social and Communication Disorders Checklist (SCDC), which measures social and communication skills.

Mothers were classified according to their level of adherence to a healthy diet into low, medium, and high adherence groups. A healthy prenatal diet (HPDP) was defined as including fruits, vegetables, nuts, whole grains, and fish. Lower adherence to the HPDP was defined as foods high in fat and refined sugar.

Mothers who had a healthy diet had children with a reduced risk of autism compared to those who had low adherence. Overall, mothers who had a healthy diet during pregnancy were more likely to have higher levels of education, were older, were more likely to be non-smokers, and to have used prenatal vitamins during pregnancy.

In the MoBa cohort, there was a 24% reduction in the risk of social communication difficulties among children born to mothers with high adherence compared to those born to mothers with the lowest adherence. For the ALSPAC cohort, there was a similar reduction in risk at age eight.

Women showed a greater reduction in risk than men. Note that girls often develop communication skills earlier than boys, which may contribute to this observed difference.

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

Both the SCQ and SCDC are used to screen for autism; however, only the SCDC measures social communication skills. Furthermore, at age three, the SCQ-RRB cannot differentiate autism from non-autistic conditions, whereas the SCQ-SOC can.

We estimated that only about one-fifth of children with high SCQ scores at age three continued to have high scores at age eight.

The risk of having a child diagnosed with autism or who has difficulty socially communicating was lower among mothers who consumed a healthy prenatal diet. However, repetitive and restrictive behavioral traits, although associated with autism, did not show similar associations.

The study's findings complement previous studies with inconsistent results. The use of different scales in the current study also allows the researchers to identify potential sources of these differences, such as the age of assessment or the subsectors used.

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