Core Revision
Revision aid, not clinical advice. This page is educational material written for exam preparation. It is not a substitute for the current guideline or for clinical judgement, and must not be relied on for the care of any individual. Always check up-to-date national guidance and verify independently before acting on anything here.
The Paediatric Reasoner
Child development is hard to memorise as a list — so don’t. Here you’ll see the four trajectories, learn the one idea that makes the ages make sense (the limit age is the referral line), read the NICE fever traffic light the way a clinician does, and drill the safeguarding red flags (NICE CG89 for the alerting features, NG76 for the referral) that must always stop you. Then the tool remembers what you find hard and brings it back until it sticks. Revision aid, not clinical advice — always check the current guideline before treating real patients.
Understand mode: the frameworks behind child development — four trajectories, the limit-age idea, the fever traffic light, and the red flags.
The one idea · milestones are four trajectories, not one list
Development runs along four separate tracks at once — gross motor, fine motor & vision, speech/language & hearing, and social/self-care — and each has its own logic. Learn the shape of each track and the ages stop being random. Movement travels head to toe and centre to edge; sounds go from cooing to words to sentences; play goes from smiling to pretending.
Then add the single most useful concept in the whole topic: the limit age. The median age is when half of children can do something; the limit age is when nearly all should — so the limit age, not the average, is the referral line.
Tap any track to see how it develops and where its referral flags sit.
Median vs limit age — the rule the exam loves
Median age = half of children can do it. Limit age = nearly all should — and that is the line at which you refer. Keep these four limit ages on a card:
One caveat that stops over-referral: correct for prematurity up to age 2. A baby born 8 weeks early is judged at their corrected age.
⚑ Always red — never a normal variant
- Regression. Losing a skill once gained (“used to be able to, now can’t”) is never normal at any age — NICE NG62 lists it as a reason for referral to paediatric neurology. It points to neurodevelopmental or metabolic disease.
- Hand preference before 12 months (corrected). An early, fixed hand preference suggests a hemiplegia on the weaker side (NICE NG62).
- Bruising in a baby who is not independently mobile. With no medical cause and no suitable explanation, NICE CG89 says suspect maltreatment.
Fourteen cards: memory hooks and always-red rules
Get these and most milestone questions answer themselves. Tap a card to flip it.
Review the cards that are due
Think of the answer, reveal it, then rate yourself — the cards you find hard come back sooner. Progress is saved on this device.
At a glance · the map, then a self-test
Two interactive maps. First the milestone grid — every domain across the ages, with the referral flags marked in red; tap any cell for the detail, or switch on Test me to predict the age. Then the NICE fever traffic light — tap a feature to see why it sits where it does, or test yourself to classify it green, amber or red.
The milestone grid & limit ages
Domains down the side, ages across the top. Red cells are the limit-age / referral flags. Tap any cell for detail; tap a domain to see its trajectory.
Ages are typical UK teaching values for revision; correct for prematurity up to age 2. Red = a limit age / referral flag.
The fever traffic light (under 5s)
Pick a band to read what it means and the features that place a child in it — tap a feature for the detail. Or switch to Test me and classify each feature green, amber or red.
Fever traffic-light features are from NICE NG143 (fever in under 5s). This is a revision summary, not the full guideline.
Spot the unwell child. Read a short vignette and decide — is this within normal limits, or a red flag that needs action? Commit your answer first, then reveal the reasoning. This is thinking like a clinician, not looking it up.
Two phrases should always stop you
In a paediatric stem, react to two things above all else: “used to be able to, now can’t” (regression) and “a baby who is not yet mobile but is bruised.” Neither is ever a normal variant — one points to neurodevelopmental or metabolic disease, the other to safeguarding. Learn the limit ages, but let those two phrases trigger an automatic alarm.
Save your progress — and go further
Your work in this tool is saved on this device. Create a free account to get started with Core Revision; the full question banks are part of membership. The tool stays free either way.
Take this further
This tool is free. If you are preparing for the MRCGP AKT, the full course puts the same reasoning into exam-style questions: a question bank with Core Lens and Deep Dive explanations, a Core Calendar revision plan built around your exam date, and Core Compass to show you which topics need you next.
Preparing for the MSRA instead?
Questions? Email admin@corerevision.com
Fever traffic light based on NICE NG143 (fever in under 5s). Referral flags: NICE NG62 (motor) and the Oxford Handbook of Paediatrics red-flag list; typical ages are standard UK teaching values. Sources last checked October 2026. A revision aid — it must not be relied on for the care of any individual; verify independently against current guidance.
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Core Revision Ltd is an independent educational platform and is not affiliated with the RCGP.
Written by practising UK GPs for exam revision. Sources are cited on this page and corrections are logged. Education only — always confirm against current guidance. Core Revision is an independent revision resource.