High adherence to a healthy prenatal dietary pattern was associated with a 22% lower likelihood of autism diagnosis in offspring and reduced odds of social communication difficulties at ages 3 and 8 years, according to data from a large cohort study.
Published in JAMA Network Open, the study included 84,548 mother-infant dyads (mean maternal age = 30.2 years; 51.2% male offspring) from the Norwegian Mother, Father, and Child Cohort Study (MoBa) and 11,670 dyads (mean maternal age = 27.9 years; 51.3% male offspring) from the Avon Longitudinal Study of Parents and Children (ALSPAC) in England. Maternal adherence to a healthy dietary pattern during pregnancy was categorized as low, medium, or high based on food frequency questionnaire responses. Autism diagnosis in offspring was obtained from the Norwegian Patient Registry in MoBa. Autism-associated traits, including social communication difficulties and restrictive/repetitive behaviors, were assessed using the Social Communication Questionnaire (SCQ) at ages 3 and 8 years in MoBa and the Social Communication Disorders Checklist (SCDC) at age 8 years in ALSPAC.
A healthy dietary pattern was characterized by high intake of fruits, vegetables, fish, nuts, and whole grains and low intake of red/processed meats, sugar-sweetened beverages, and refined carbohydrates. Mothers in the highest adherence group had higher intakes of key nutrients such as folate, vitamin D, and omega-3 fatty acids compared to those in the lowest adherence group. Nutrient intakes among those with high adherence aligned with national dietary recommendations in Norway and England.
The proportion of children with high scores on autism-related traits was consistently higher in the lowest dietary adherence group. For example, in MoBa, 1.4% of children in the lowest adherence group had an autism diagnosis, compared to 1.0% in both the medium- and high-adherence groups.
In fully adjusted models, high vs low adherence to a healthy prenatal diet was associated with lower odds of an autism diagnosis (odds ratio [OR], 0.78; 95% confidence interval [CI], 0.66-0.92) and social communication difficulties at age 3 years (OR, 0.76; 95% CI, 0.70-0.82) in MoBa and age 8 years in ALSPAC (OR, 0.74; 95% CI, 0.55-0.98). Associations were less consistent for restrictive/repetitive behaviors and SCQ scores at age 8 years.
Subgroup analyses revealed that a plant-based dietary pattern was associated with lower odds of high SCQ scores at age 8 years (OR, 0.92; 95% CI, 0.86-0.99) and social communication difficulties at age 8 years (OR, 0.89; 95% CI, 0.82-0.96) in MoBa. The association between high adherence to a healthy prenatal diet and lower social communication difficulties at age 8 years was stronger in female offspring (MoBa: OR, 0.83; 95% CI, 0.73-0.95; ALSPAC: OR, 0.62; 95% CI, 0.40-0.97) than male offspring (MoBa: OR, 1.00; 95% CI, 0.88-1.13; ALSPAC: OR, 0.84; 95% CI, 0.58-1.21).
The study's strengths include its large sample size, prospective design, detailed dietary assessment, and analysis of autism diagnosis and traits. Its limitations include potential for residual confounding, selection bias due to missing outcome data, and measurement error in dietary- and autism-related assessments.
"These findings highlight the association between prenatal diet and offspring autism-related outcomes and contribute to the evolving understanding of autism etiology," the authors wrote. They noted that further research is needed to substantiate the results and explore potential causal mechanisms.
One study investigator reported grants from the UK Prevention Research Partnership and NIHR outside the submitted work. No other disclosures were reported.