Developmental milestones
Development unfolds as a predictable, ordered sequence across four domains, so comparing a child against expected order (not just a single skill) is what turns a routine check into a screening tool for underlying problems.
First principles
Development is tracked across four separate domains
Developmental surveillance divides a child's skills into four domains that mature in parallel but not always at the same rate: gross motor (posture and large movement: head control, sitting, walking, running), fine motor and vision (hand use, grasp, drawing, and how vision guides these), hearing, speech and language (sound response, babble, words, sentences), and social, emotional and behavioural development (smiling, attachment, play, interaction). Separating development into domains matters because delay is rarely uniform: a child can be behind in one domain and entirely normal in the others, and the pattern of which domain is affected points toward a different underlying cause each time.
Educational content pending clinical review. Not medical advice.