Head circumference trends in autism between 0 and 100 months.
Head-size extremes in autism show up at clear, sex-specific ages—track them to catch risk early.
01Research in Context
What this study did
Crucitti et al. (2020) pooled every paper that measured head size in kids with autism. They looked at birth to 100 months and split the data by age band and sex.
The review gives a clear map of when heads are unusually big or small.
What they found
Boys with autism often start with large heads at birth and again between 5 and 8 years.
Girls show a different path: smaller heads at 12–17 months, then some swing to very large heads at 3–5 years.
These sex-specific windows matter for red-flag checks.
How this fits with other research
Ben-Itzchak et al. (2020) followed the same kids from toddler to teen. They show that early skills, not head size, predict long-term gains. The two papers pair well: Joel flags when to look, Esther tells what to watch next.
Amaria et al. (2012, 2018) tracked adaptive skills for up to 15 years. Most kids stayed on a low curve no matter their head size. Together the work says: head extremes are a clue, not a verdict.
Wang et al. (2022) found brain-stem hearing tests in 6-month-olds predict autism. Adding head-circumference checks at well-baby visits gives two cheap, early screens.
Why it matters
You can spot risk faster. Measure head at birth, 12, 24, 36 months and again at school entry. Mark any jump above or below the normal band. If you see macrocephaly in a toddler boy or microcephaly in a 1-year girl, move up your autism screen and share the chart with the pediatrician. It takes 30 seconds and costs nothing.
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02At a glance
03Original abstract
Summaries of studies that have measured head size in those with autism, known as meta-analyses, currently exist. However, this approach does not adequately explain extreme cases (such as those with extremely small, or extremely large, head size). Because of this, we obtained all available published data measuring head size (12 studies). The data from each study were then combined to make a larger dataset. We found that females with autism aged 12-17 months had, on average, smaller head sizes. Otherwise, average head size was not atypical in autism. However, we found that males with autism were more likely to have extreme head sizes at birth and between 60 and 100 months, a small head between 6 and 11 months, and a large head between 12 and 17 months. Females with autism were more likely to have extreme head sizes between 36 and 59 months and were less likely at birth. Our approach was able to measure the influence of age and biological sex on head size in autism, as well as the frequency of extreme cases of head size in autism. These results add to what we already know about head size in autism.
Autism : the international journal of research and practice, 2020 · doi:10.1177/1362361320921037