The bottom line: Tracking how babies grow over their first year reveals that persistently very small or very large head and height patterns are linked to a higher risk of autism. For families and clinicians, this shows why repeated growth measurements matter more than single check ups when monitoring early neurodevelopment and mental health risk. In healthcare practice and public policy, the findings support closer use of routine infant growth data to guide earlier follow up, targeted monitoring, and timely support where concerns emerge.
Subtle differences in how babies grow during their first year may offer early clues about autism risk, according to new research tracking infant development from birth. The findings, published in Autism Research, suggest that both unusually small and unusually large head growth patterns are linked to a higher likelihood of autism, particularly when these patterns reflect broader physical growth rather than head size alone.
The motivation for this study arose in response to the long standing question in autism research regarding early biological markers that may precede a formal diagnosis. As Idan Menashe, PhD, professor at the Ben Gurion University of the Negev, explained: “While autism spectrum disorder (ASD) is typically diagnosed in early childhood, the underlying neurodevelopmental processes are thought to be activated much earlier. Head circumference is a simple, cost effective clinical measure routinely collected throughout infancy and early childhood that may reliably serve as a proxy for brain growth.”
The study followed hundreds of children from birth through routine health checks in their first year of life, focusing on head circumference and height as markers of early development. Rather than relying on a single measurement, researchers examined how growth unfolded over time, capturing patterns that are often missed in standard check ups. According to Menashe: “Previous studies assessing head circumference to ASD have yielded inconsistent results, often due to reliance on a single time point measurement and small sample sizes.”
By making use of a large, population based cohort with repeated head circumference measurements throughout infancy, the researchers aimed to identify distinct growth trajectories that may be associated with a subsequent diagnosis of autism. “This approach allowed us to gain a clear understanding of the dynamic nature of early growth in relation to neurodevelopmental outcomes,” Menashe said.
Infants whose head size consistently fell at the very low or very high ends of the growth chart were significantly more likely to later receive an autism diagnosis than those whose growth stayed within the typical range. The strongest associations were seen among babies at the most extreme ends, including those with very small or very large head measurements throughout infancy. Reflecting on this, Menashe noted: “A major finding of the study was that children with consistently high or low head circumference, particularly those falling within the most extreme percentiles, had a higher risk of later being diagnosed with ASD.”
Importantly, the research found that head growth did not act in isolation. Head size and height were closely linked across the first year, and the increased autism risk was most pronounced when both followed similar atypical trajectories. Menashe highlighted that these results suggest a broader developmental pattern, stating that “these associations were particularly pronounced in children with similar height trajectories, suggesting that atypical head circumference in ASD may reflect a generalised physiological growth dysregulation.”
Previous studies have often focused on rapid head growth as a potential early marker for autism, especially in babies born with average head size who then show accelerated growth. While this pattern was observed, it accounted for only a portion of the increased risk. Consistently small or large growth patterns appeared to carry a clearer association, reinforcing the value of long term monitoring rather than one off measurements.
The research drew on detailed health records from routine infant clinics, where growth is measured at regular intervals during the first year. This allowed researchers to identify distinct growth trajectories and compare outcomes between children later diagnosed with autism and those who were not. By excluding premature births and focusing on children with complete data, the analysis aimed to provide a clearer picture of typical and atypical development.
The findings also help explain why earlier research has produced mixed results. Many children with autism show no unusual growth patterns at all, while others display changes that may be subtle or temporary. By looking at growth as a process rather than a snapshot, the study offers a more nuanced understanding of how physical development relates to neurodevelopmental outcomes.
While the authors stress that growth patterns alone cannot be used to diagnose autism, the findings support the value of longitudinal growth data in early childhood. As Menashe cautioned: “While this study alone cannot determine whether head circumference should be used as a screening tool for ASD, it does support the value of longitudinal growth data in early childhood.” He added that “measuring growth parameters throughout infancy may help in establishing a more comprehensive developmental risk profile and improving early monitoring techniques.”
The study adds to growing evidence that autism is biologically diverse, with different developmental pathways leading to similar behavioural outcomes. Looking ahead, Menashe said: “Future research will focus on examining whether these growth trajectories are associated with specific autism phenotypes, including cognitive, behavioural, and developmental traits and the biological mechanisms underlying these intriguing autism subgroups.” He concluded that “ultimately, this research may help advance more targeted early identification strategies for individuals with certain subsets of ASD.”
