Learn the Signs. Act Early.

The CDC's "Learn the Signs. Act Early." programme is a quiet public-health gem. It started in the early 2000s with a simple premise: parents are the best observers of their own children, and most developmental concerns are missed not because parents didn't notice something but because they weren't sure what to notice or what to do with it. The programme is a free, plain-language toolkit for closing that gap.

This piece walks through the CDC milestones programme, the M-CHAT-R/F screening tool many paediatricians use, what the assessment journey actually looks like, how to navigate long waitlists, and what to do in the meantime.

What's in it Two main things: milestone checklists for each age, and what to do if something on a checklist is missing.

The checklists run from two months to five years and cover four areas: social and emotional, language and communication, cognitive learning, and movement and physical development. Each milestone is described in concrete behaviour ("smiles back when you smile"), not in jargon. There is no diagnostic claim attached — the question is always "does my child do this?" with a clear path if the answer is "not yet."

The "what to do" guidance is just as plain. The recommendation is to print the checklist, fill it in, bring it to the next well-child visit, and ask. Doctors can act faster when parents bring specifics rather than worries.

The M-CHAT-R/F: what your paediatrician is using At the 18- and 24-month well-child visits in the US (and increasingly globally), many paediatricians administer the Modified Checklist for Autism in Toddlers, Revised, with Follow-Up (M-CHAT-R/F). It is a 20-question parent-report screener.

How it works: 1. Parents answer 20 yes/no questions about their toddler's behaviour — pointing, sharing interest, response to name, pretend play. 2. The questionnaire is scored. A score of 0–2 is low concern; 3–7 is medium concern; 8+ is high concern. 3. For medium-concern scores, the M-CHAT-R is paired with a structured follow-up interview (the "F" part) that asks for examples and clarifications. This second step substantially reduces false positives. 4. After the follow-up, children flagged at medium or high concern are referred for a formal developmental evaluation.

The M-CHAT-R/F is a screening tool, not a diagnosis. A positive screen means "worth a deeper look," not "your child is autistic." Sensitivity is high — about 85% — but the positive predictive value depends on the population; the follow-up interview is part of why this tool is the current standard.

The AAP has recommended universal autism-specific screening at 18 and 24 months since 2007, and reaffirmed that recommendation in 2020 in *Pediatrics*. If your paediatrician has not run the M-CHAT-R/F by 24 months, asking for it is reasonable.

Red flags by age band The CDC milestones are organised by age. A short version of what tends to bring autism into the conversation:

By 9 months: little response to name, limited sharing of facial expressions, not turning toward the person speaking, persistent loss of eye contact.

By 12 months: no babbling, no back-and-forth gestures (pointing, showing, reaching, waving), inconsistent response to name, very limited expression of emotion in response to others.

By 16 months: no spoken words, no functional gestures (pointing to share, showing things to a caregiver), reduced or unusual eye contact during interaction.

By 18 months: no two-word phrases, no pretend play, regression in any previously-acquired social or language skill. Regression is particularly important: a child who used words and stopped warrants prompt evaluation.

By 24 months: limited spontaneous two-word phrases, reduced interest in other children, very limited imaginative play, marked sensory aversions interfering with daily life.

These are individual signs. A single one rarely means very much — most children miss some milestones at some point. Clinicians look at the pattern across several areas.

How to use it without making yourself anxious Every developmental checklist has the same hazard: a parent reads it, realises their toddler doesn't reliably wave bye-bye, and spirals. A few things to keep in mind: - Most milestones have wide normal ranges. The checklists list ages where most children have a skill, not the latest acceptable age. - A child can be ahead in some areas and behind in others. A "spiky profile" is normal in development and especially common in autistic children. - Missing a single milestone is rarely meaningful on its own. Patterns across several areas, or losing skills the child used to have, are what clinicians look at.

Why early matters (without overstating it) The early years are when the brain is most flexible, and supports that arrive earlier often need to do less work than the same supports later. That is the "early" in Learn the Signs. Act Early. But earlier is better is not the same as later is too late — children and teens continue to learn and grow, and families who didn't catch something at two are not behind for life. They just have catching up to do, and the catching up is real and possible.

A note on the autism milestones Some milestones on the CDC list are particularly worth flagging — not because their absence means autism, but because their absence brings autism into the conversation. Pointing to share something (not just to request), looking at faces to read emotions, responding to their own name, gesturing along with words. Absence at the expected age is not a diagnosis. It is a reason to ask.

The assessment journey: what to expect If a screening flags concern, the next step is a formal developmental evaluation. This is usually run by:

• A developmental paediatrician (medical doctor with extra training in child development), or
• A child psychologist (clinical psychologist with autism specialism), or
• A multidisciplinary team combining the above plus a speech-language pathologist and sometimes an occupational therapist.

A full evaluation typically involves: 1. Parent interview — usually a structured interview like the Autism Diagnostic Interview-Revised (ADI-R), covering developmental history, current behaviour, and family observations. This is the longest part, sometimes 90+ minutes. 2. Structured observation of the child — often the Autism Diagnostic Observation Schedule (ADOS-2), a play-based assessment in which the clinician offers a series of prompts and observes the child's social communication, play, and behaviour. 3. Language and cognitive testing — usually administered by the SLP and/or psychologist. 4. Written report and feedback session — the family receives a written diagnostic report and a meeting to walk through findings and next steps.

Total time across appointments: typically 4–8 hours spread over 2–4 visits. The report usually arrives 2–4 weeks after the final session.

Navigating long waitlists In most countries, public-system autism assessment waitlists are long — 6 months to 2 years is not unusual. This is a system problem, not a family problem, but the wait can feel passive and frightening.

Options that often shorten it:

• Ask for the waitlist in writing, with an estimated date. This sometimes prompts the service to give an earlier slot if one opens up.
• Get on multiple lists if your area has more than one assessment route (e.g., NHS plus an academic centre, or public plus a charity-run service). You can withdraw from one once another comes through.
• Private assessment, if it is affordable. Most private diagnostic reports are recognised by schools and disability services, though the rules vary by country. Ask your paediatrician what is accepted locally.
• Telehealth assessments have expanded in recent years and sometimes have shorter waits.

What to do in the wait The waitlist period is not "do nothing time." A lot can happen in those months:

• Start speech-language and occupational therapy now if the child would benefit. Most therapy referrals do not require a formal autism diagnosis. Early support has its own evidence base regardless of the eventual diagnostic outcome.
• Document. Short notes on what you observe, dated. The clinician at the assessment will ask for examples; specifics are easier to bring than memories.
• Read by autistic adults, not just about autism. Books and blogs from autistic adults give a fuller picture than clinical descriptions alone.
• Connect with other parents in the same waiting room. Peer support during a long wait is genuinely protective.

A diagnosis is a piece of information, not a verdict, and it does not change who your child is. The right supports almost always start before the diagnosis arrives.