Signs of autism in babies — what can and cannot be seen before 12 months

Why this page exists

The most searched version of this question is “signs of autism in a two-month-old”. The honest answer is that there are none, and a page that invents some would be doing a frightened parent real harm.

But the question behind the question is a fair one, and it deserves better than being waved away. Parents ask it because something feels different, or because an older child was diagnosed late and they do not want to lose the same time twice. That is a reasonable instinct. This page is about what you can actually do with it.

What is knowable, and when

Autism is a description of a pattern of development. A pattern needs time to become visible, which is why no tool exists to identify it in a young baby, and why autism-specific screening does not usually begin until 18 months at the earliest.

That does not leave you with nothing to watch in the first year. It means what you are watching is general development rather than autism specifically. Response to name, shared smiles, back-and-forth sounds, following your gaze, gestures like waving and pointing — these are ordinary developmental milestones. When they do not arrive on time, that is worth acting on regardless of what the eventual explanation turns out to be. Often it is not autism. Sometimes it is hearing. Sometimes it resolves on its own.

What the infant-sibling research does and does not say

You may come across studies that followed babies who had an autistic older sibling, and reported differences appearing across the first year. Those studies are real and useful, and they are routinely over-read.

What they found were average differences between groups, measured with research instruments, often only visible when many babies were pooled. That is a very different thing from a sign you can observe in your own baby on a Tuesday afternoon. Group averages do not diagnose individuals, and no responsible clinician would try.

The practical takeaway from that literature is not a checklist. It is that having an autistic older sibling raises the likelihood enough that your pediatrician should be watching development closely and screening on schedule — not that your baby’s development can be read for early answers.

What you can do now

Three things are available to you today, and none of them requires a diagnosis or even a firm suspicion.

Get hearing checked. This is the step most often skipped and most often useful. A baby who does not turn to their name may not be hearing it. Glue ear is common, treatable, and produces exactly the pattern that worries parents most.

Write things down with dates. Not a diary of anxieties — a short factual note of what you noticed and roughly when. This is the single most useful thing you can bring to an appointment, and it is much harder to reconstruct later.

Refer to early intervention. In the US, if your child is under 3, you can contact your state’s early intervention programme yourself. You do not need a diagnosis, a referral, or anyone’s permission. Support is based on developmental need, not on a label.

If you are told to wait and see

Wait and see is sometimes reasonable advice delivered badly. The useful version has a date and a specific thing to look for attached: by this age, I would expect to see this; if you do not, come back.

If you are given the vague version, ask for the specific one. And in the meantime, watching and acting are not alternatives — a hearing check and an early intervention referral cost you nothing if the concern turns out to be nothing.

Where this goes next

If your child is older than the ages on this page, the pattern-by-pattern account lives on signs by age. If you are already past the point of wondering and want to know how assessment actually works, start with getting a child assessed.