A prospective study of fetal head growth, autistic traits and autism spectrum disorder.
Fetal head size does not predict autism, but head growth trends during the first year do.
01Research in Context
What this study did
Doctors measured baby head size inside the womb. They used regular pregnancy ultrasound scans.
They tracked two groups of mothers. One group was in the Netherlands, the other in the UK.
What they found
In the Dutch group, smaller head size at 20 weeks weakly linked to more autism traits at age 6.
In the UK group, the same link did not show up. When both groups were combined, the signal vanished.
How this fits with other research
Balaum et al. (2026) looked after birth. Babies whose head size stayed in the top or bottom 5 % during the first year had 6–9 times higher autism odds. The post-natal signal is strong; the pre-natal signal is not.
Geurts et al. (2008) studied baby brothers and sisters of children with autism. They also found a clear pattern, but only over the study period of age. Again, the action seems to be after birth, not before.
Jennett et al. (2003) showed that children who already have autism and big heads often score high on non-verbal tests. That paper looked at older kids, not babies in the womb.
Why it matters
Stop using a single 20-week head measure as an autism screen. The number is not reliable enough. Instead, track head growth across the first year, especially in high-risk siblings. Flag infants who jump or drop across percentile lines and pair that data with eye-contact and social smiling checks.
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02At a glance
03Original abstract
UNLABELLED: Altered trajectories of brain growth are often reported in Autism Spectrum Disorder (ASD), particularly during the first year of life. However, less is known about prenatal head growth trajectories, and no study has examined the relation with postnatal autistic symptom severity. The current study prospectively examined the association between fetal head growth and the spectrum of autistic symptom severity in two large population-based cohorts, including a sample of individuals with clinically diagnosed ASD. This study included 3,820 children from two longitudinal prenatal cohorts in The Netherlands and Australia, comprising 60 individuals with a confirmed diagnosis of ASD. Latent growth curve models were used to examine the relationship between fetal head circumference measured at three different time points and autistic traits measured in postnatal life using either the Social Responsiveness Scale or the Autism-Spectrum Quotient. While lower initial prenatal HC was weakly associated with increasing autistic traits in the Dutch cohort, this relationship was not observed in the Australian cohort, nor when the two cohorts were analysed together. No differences in prenatal head growth were found between individuals with ASD and controls. This large population-based study identified no consistent association across two cohorts between prenatal head growth and postnatal autistic traits. Our mixed findings suggest that further research in this area is needed. Autism Res 2018, 11: 602-612. © 2018 The Authors Autism Research published by International Society for Autism Research and Wiley Periodicals, Inc. LAY SUMMARY: It is not known whether different patterns of postnatal brain growth in Autism Spectrum Disorder (ASD) also occurs prenatally. We examined fetal head growth and autistic symptoms in two large groups from The Netherlands and Australia. Lower initial prenatal head circumference was associated with autistic traits in the Dutch, but not the Australian, group. No differences in head growth were found in individuals with ASD and controls when the data was combined. Our mixed findings suggest that more research in this area is needed.
Autism research : official journal of the International Society for Autism Research, 2018 · doi:10.1038/mp.2016.213