Infant Development 0-12 months

Infant development follows a cephalocaudal (head-to-toe) and proximodistal (center-to-periphery) sequence. At 2 months, the infant lifts the head prone and produces a social smile — the first major social milestone. By 4 months, head control is steady, rolling begins (back to front typically first, front to back by 5-6 months), and coos become reciprocal. At 6 months, sitting with support, babbling with consonant sounds ("bababa"), and grasping/mouthing objects emerge; transferring objects hand-to-hand follows around 6-7 months. By 9 months, the infant sits unsupported, crawls, develops a pincer grasp (thumb-to-finger), and demonstrates stranger anxiety — a sign of healthy attachment and object permanence (Piaget's sensorimotor stage). At 12 months, expect 1-3 words, pulling to stand, cruising furniture, and a refined pincer grasp. Weight triples and length increases roughly 50% by age one. Anterior fontanelle remains open until 12-18 months; premature closure warrants investigation. Erikson's stage is trust versus mistrust — consistent caregiver response to crying builds trust. Introduction of solids begins around 6 months when the extrusion reflex fades and the infant can sit with support. Nursing assessment compares milestones to expected ranges and screens using validated tools (e.g., ASQ) at 9 and 12 months.