Early Signs of Autism in Babies and Toddlers

What are the early signs of autism?

The early signs of autism are mostly differences in social communication: how a baby or toddler responds to people, shares attention, uses gestures and plays. The NHS describes the main signs as "differences in how someone communicates, behaves and reacts compared to those who are not autistic", and adds the sentence every list should start with: "Every autistic person is different and many autistic people will not show all the signs of autism, or signs may not always be obvious."

The American Academy of Pediatrics (AAP) explains why early signs are easy to miss. Autistic children "usually sit, crawl, and walk on time", so "the subtler differences in the development of gestures (pointing), pretend play and social language often go unnoticed by families and doctors."

Signs of autism in babies under 1

Most listed signs cannot be seen in the first few months. A prospective study led by Sally Ozonoff at the University of California, Davis, filmed 25 babies later diagnosed with autism and 25 typically developing babies at 6, 12, 18, 24 and 36 months. At 6 months, gaze to faces, shared smiles and sounds directed at others were "highly comparable between groups". Differences emerged as those behaviours declined, and were significant by 12 months on most measures.

In other words, at 6 months smiling and watching faces did not separate the two groups, and a single quiet day tells you little. The earliest ages on the US Centers for Disease Control and Prevention (CDC) list are 9 months: a child who "does not respond to name by 9 months of age" or "does not show facial expressions such as happy, sad, angry, and surprised by 9 months of age".

By 12 months the AAP describes a clearer difference in joint attention. Most children "can immediately look in the direction of an object a parent is pointing at", then look back at the parent. A child on the autism spectrum "may appear to ignore the parent", which, the AAP notes, can make parents worry about hearing. See a baby not making eye contact and a baby not responding to sound.

Signs of autism in toddlers, by age

The CDC lists these social communication signs with an age attached:

The AAP adds that by 15 months most children point to out-of-reach things they want, while an autistic child "may instead take a parent's hand and lead the parent to the object". See a baby not pointing yet for the two kinds of pointing.

Behaviour signs on the CDC and NHS lists include lining up toys and getting upset when the order changes, repeating words or phrases (echolalia), flapping hands, rocking or spinning, strong reactions to sounds, smells, tastes or textures, and being upset by small changes. Any one of them can have another explanation, which is why lining things up and hand flapping and a toddler not responding to their name each have their own page.

Losing words or skills

The AAP says about 25% of children later diagnosed with autism may develop some language they then stop using, typically between 15 and 24 months, sometimes becoming more socially withdrawn. NICE's guideline for England tells professionals to refer children younger than 3 to the autism team if there is regression in language or social skills. Losing motor skills at any age goes to a paediatrician first. More on a baby who has lost a skill.

What is not a sign of autism, and what does not rule it out

• One behaviour on its own. NICE asks professionals to consider autism when there are concerns, "but be aware that there may be other explanations for individual signs and symptoms."
• Walking late is not a typical early sign. The AAP notes autistic children usually reach sitting, crawling and walking on time.
• Good eye contact does not rule autism out. NICE says not to rule out autism because of "good eye contact, smiling and showing affection to family members", or because of reported pretend play or normal language milestones.
• Hearing comes first. Not responding to a name can be a hearing problem. Among the AAP's steps while you wait for an assessment is asking whether your child's hearing has been checked.

How assessment works in the UK and the US

UK. The NHS says to speak to a GP if you think your child might be autistic; if your child is not yet at school, a health visitor may need to make the referral. NICE says the diagnostic assessment should start within 3 months of referral to the autism team, but the NHS is candid that "it can take a few months or longer". In England, Right to Choose may let you pick a service with a shorter wait. The team may ask about development, watch your child play with you and read reports from nursery.

US. The AAP recommends autism screening for all children at the 18- and 24-month well-child checkups. A common tool is the M-CHAT-R/F, in which parents answer 20 yes/no questions in under 5 minutes, with follow-up questions if the score is raised. In its validation study of 16,071 toddlers, children who screened positive after follow-up had a 47.5% risk of an autism diagnosis and a 94.6% risk of some developmental delay or concern. A positive screen means "assess further", not "autistic". The AAP says children under 3 should also be referred to the state Early Intervention programme.

NICE adds that a negative score on any screening tool "does not rule out autism".

When to speak to your GP, health visitor or doctor

• Straight away if your child has lost words, babble, gestures or social skills they used to have.
• If you notice several of the signs above together, rather than one in isolation.
• Whenever you are worried. NICE tells professionals to take parents' concerns seriously "even if these are not shared by others". If a referral is hard to get, the NHS says you can ask for a second opinion.

The wider picture is in when to worry about development, and baby sign language explains what early signing does and does not change.

Frequently asked questions

Can you see signs of autism in a 4-month-old baby?

Usually not reliably. In a prospective study, babies later diagnosed with autism looked at faces, smiled and made sounds to others about as often as other babies at 6 months, and differences became clear by 12 months. If something worries you at any age, raise it, but a 4-month-old's behaviour alone rarely answers the question.

What are signs of autism in a 9-month-old?

The CDC lists two at 9 months: not responding to their name, and not showing facial expressions such as happy, sad, angry and surprised. Check hearing too, since a baby who cannot hear well will not turn to their name. One sign is a reason to ask, not a diagnosis; NICE notes individual signs can have other explanations.

Are the signs of autism different in girls?

They can be harder to see. The NHS says autistic girls may copy how other children behave and play, be quiet in situations they find difficult, appear to cope socially and show fewer repetitive behaviours. NICE warns that autism "may be under-recognised in girls leading to underdiagnosis", so describe what you see at home in detail.

Is there a test for autism in babies?

There is no single test. In the US, the AAP recommends screening at 18 and 24 months, often with the M-CHAT-R/F parent questionnaire, and a positive result leads to further assessment rather than a diagnosis. In the UK, diagnosis comes from an assessment by a team that looks at development, play and history.