pediatrics
Physical Growth of Infants and Children
Length
Length is measured with a supine stadiometer in an infant. The infant is laid on the stadiometer. The infant's head is held so that the crown is flat against the head plate. Gently, the infant's legs are straightened and the knees are pressed down. Then the foot plate is moved until it touches the infant's heels. Three measurements should be taken and averaged to determine an accurate length measurement. Height is measured with a standing stadiometer once a child can stand. The child stands against the stadiometer. The child's feet should be flat on the floor and the heels flat against the wall. The child's head should be positioned so that the eyes are parallel to the floor. Then the head plate of the stadiometer is brought down to touch the crown of the head. Again, three measurements should be taken and averaged to determine an accurate height measurement. In general, length in full-term infants increases about 30% by 5 months and>50% by 12 months. Infants grow about 25 cm during the first year, and height at 5 years is about double the birth length. Most boys reach half their adult height by about age 2 years; most girls reach half their adult height at about age 19 months. Rate of change in height (height velocity) is a more sensitive measure of growth than time-specific height measurements. In general, healthy term infants and children grow about 2.5 cm/month between birth and 6 months, 1.3 cm/month from 7 to 12 months, and about 7.6 cm/year between 12 months and 10 years. Before 12 months of age, height velocity varies and is due in part to perinatal factors (eg, Preterm Infants ). After 12 months, height is mostly genetically determined, and height velocity stays nearly constant until puberty; a child’s height relative to peers tends to remain the same. In general, boys weigh more and are taller than girls when growth is complete because boys have a longer prepubertal growth period, increased peak velocity during the pubertal growth spurt, and a longer adolescent growth spurt. Some Small-for-Gestational-Age (SGA) Infant tend to be shorter throughout life than infants whose size is appropriate for their gestational age. Boys and girls show little difference in height and growth rate during infancy and childhood. Extremities grow faster than the trunk, leading to a gradual change in relative proportions; the crown-to-pubis/pubis-to-heel ratio is 1.7 at birth, 1.5 at 12 months, 1.2 at 5 years, and 1.0 after 7 years. 