Growth and Development (2 months – 1 year)
Length is measured in children too young to stand; height is measured once the child can stand. In general, length in normal-term infants increases about 30% by 5 months and > 50% by 12 months; infants grow 25 cm during the 1st yr, and height at 5 yr is about double the birth length.
In most boys, half the adult height is attained by about age 2; in most girls, height at 19 mo is about half the adult height.
Weight follows a similar pattern. Full term babies generally lose 5 to 8% of birth weight in the days after delivery but regain their birth weight within 1-2 weeks. They then gain 14 to 28 g/day until 3 months, then 4000 g between 3 and 12 months, doubling their birth weight by 5 months, tripling it by 12 months, and almost quadrupling it by 2 years of age.
Head circumference reflects brain size and is routinely measured and charted until 36 months. At birth, the brain is 25% of adult size, and head circumference averages 35 cm. Head circumference increases an average 1 cm/month during the 1st yr.
Growth is rapid in the 1st 8 months, and by 12 months, is 75% of adult size. Head circumference increases 3.5 cm over the next 2 yr; the brain is 80% of adult size by age 3 yr and 90% by age 7 yr.