Infant Physical Development: Growth, Head Size, Motor & Sensory Milestones

First‑Year Physical Changes

• Growth: Weight triples; length increases ~10 inches (25 cm).
• Head circumference: Grows ~3 inches (7.5 cm); reflects brain growth.
• Body proportions: Head becomes relatively smaller vs. trunk/limbs.
• Motor milestones: Rolling (4–6 mo), sitting (6–8 mo), crawling (7–10 mo), walking (12–15 mo).
• Sensory development: Visual focus, sound localization, smell/taste discrimination.
• Teething: Typically begins 4–7 months (range 2–12 mo).

Regular well‑child visits track these milestones and identify delays early.