Developmental milestones

Gross motor, fine motor, language, and social-cognitive milestones from birth to 5 years — and when delay needs workup.

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◆When delays demand a workup

•Loss of any previously acquired skill at any age → URGENT workup (regressive autism, leukodystrophy, etc.)
•No social smile by 2 months; no babbling by 9 months; no first words by 16 months; no 2-word phrases by 24 months
•Not walking by 18 months → check CK (Duchenne), hip exam
•Hand preference before 18 months → suspect hemiparesis on opposite side
•Persistent primitive reflexes after expected disappearance (Moro >6 mo, palmar grasp >4 mo) → CNS pathology

•2 mo: social smile, lifts head 45°, follows past midline, coos
•4 mo: rolls front-to-back, laughs, looks at hand, grabs
•6 mo: sits with support, rolls both ways, transfers objects hand-to-hand, babbles ('mama' non-specific), stranger anxiety begins

•9 mo: sits without support, pulls to stand, pincer grasp emerging, says 'mama/dada' specifically, plays peek-a-boo, object permanence
•12 mo: cruises → first independent steps, 1–2 words besides mama/dada, waves bye-bye, follows one-step command
•15 mo: walks alone, 3-finger feeds self, 3–5 words, points to wants
•18 mo: runs, scribbles, ≥10 words, identifies one body part, plays alongside (parallel play emerges)

•2 yr: kicks ball, 2-word phrases, ~50 words, 50% understandable, parallel play, follows 2-step commands
•3 yr: pedals tricycle, draws circle, 3-word sentences, ~75% understandable, knows age/name/gender
•4 yr: hops on one foot, draws cross then square, 4-word sentences, 100% understandable, cooperative play
•5 yr: skips, draws triangle, prints name, asks meaning of words, has best friend

•M-CHAT screen at 18 and 24 months (autism)
•Autism red flags: no joint attention, no pointing, no pretend play, lack of social smile, repetitive behaviors
•Diagnostic eval if M-CHAT positive — refer to developmental pediatrics
•ADHD: cannot diagnose <4 years old; symptoms in ≥2 settings, ≥6 months

Age	Key milestone
2 mo	Social smile
4 mo	Rolls front-to-back, laughs
6 mo	Sits with support, babbles, stranger anxiety
9 mo	Pulls to stand, pincer grasp, 'mama/dada' specific
12 mo	First independent steps, 1–2 words
18 mo	Runs, 10+ words, identifies body part
2 yr	2-word phrases, 50 words, parallel play
3 yr	Pedals tricycle, 3-word sentences, draws circle
4 yr	Hops one foot, draws cross, cooperative play
5 yr	Skips, prints name, draws triangle

◆Loss of acquired skills at ANY age = urgent neuro workup (regression)
◆No walking by 18 months in a boy → check CK to rule out Duchenne
◆Hand preference before 18 months means hemiparesis on the OTHER side
◆Persistent Moro reflex past 6 months suggests upper motor neuron pathology
◆Autism screen at 18 + 24 months with M-CHAT; early ID + intervention improves outcomes
◆Stranger anxiety appears ~6 mo and peaks ~9 mo — REASSURE caregivers it's normal
◆Parallel play (2 yr) → cooperative play (4 yr) — common sequence question

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