The most important and sensitive indicator of a child's growth and development, reflecting nutritional status. Weight increases most rapidly during the first three months after birth, typically growing 600–1000 grams per month, ideally not less than 600 grams. From 3 to 6 months, monthly weight gain is generally 600–800 grams.From 6 to 12 months, the average monthly gain is 300 grams. After age 1, growth slows significantly, with children aged 1 to 3 gaining an average of 150 grams per month. II. Height Factors affecting growth and development in the short term have little impact on height, which is primarily influenced by genetics, ethnicity, and environment. Height increases most rapidly during the first year after birth, with an average annual gain of 25 cm.The second year sees an average increase of 10 cm, while the third year averages 4–7.5 cm of growth.
III. Head Circumference
Head circumference is a crucial indicator of brain development. At birth, the average head circumference is 34 cm; by age 1, it averages 46 cm. The second year adds 2 cm, and the third year adds 1–2 cm. By age 3, the average head circumference is 48 cm, approaching adult proportions.
IV. Chest Circumference
At birth, a child's chest circumference is smaller than their head circumference. As the child grows monthly, the chest circumference gradually catches up to the head circumference. Generally, by age 1, the chest circumference equals the head circumference. However, due to generally good nutritional status, many infants reach this equivalence before age 1. After age 1, chest circumference increases significantly faster than head circumference, gradually surpassing it.