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Physical growth refers to an increase in body size (length or height and weight) and in the size of organs. From birth to about age 1 or 2 years, children grow rapidly. After this time, growth slows. As growth slows, children need fewer calories and parents may notice a decrease in appetite. Two-year-old children can have very erratic eating habits that sometimes make parents anxious. Some children may seem to eat virtually nothing yet continue to grow and thrive. Actually, they usually eat little one day and then make up for it by eating more the next day.
During the preschool and school years, growth in height and
weight is steady. Children tend to grow a similar amount each year until
the next major growth spurt occurs in early adolescence.
Different organs grow at different rates. For example, the
reproductive system has a brief growth spurt just after birth, then
changes very little until just before sexual maturation
(puberty). In contrast, the brain grows almost exclusively during the
early years of life. The kidneys function at the adult level by the end
of the first year.
Children who are beginning to walk have an endearing physique,
with the belly sticking forward and the back curved. They may also
appear to be quite bow-legged. By 3 years of age, muscle tone increases
and the proportion of body fat decreases, so the body begins to look
leaner and more muscular. Most children are physically able to control
their bowels and bladder at this time.
Doctors report how children are growing in relation to other children their age and monitor the children's weight gain compared to their height. From birth until 2 years of age, doctors record all growth parameters in a chart by using standard growth charts from the World Health Organization (WHO). After age 2, doctors record growth parameters by using growth charts from the Centers for
Disease Control and Prevention (CDC).
Length and Height
Length in children who are too young to stand is measured while
children lie on their back on a suitable device, such as a measuring
table (called a stadiometer). Height in children who can stand is
measured using a vertical measuring scale. In general, length in
normal-term infants increases about 30% by age 5 months and more than
50% by age 12 months. Infants typically grow about 10 inches (25
centimeters) during the first year, and height at 5 years is about
double the birth length. In boys, half the adult height is attained by
about age 2. In girls, height at 19 months is about half the adult
height.
Weight
Normal-term newborns typically lose 5 to 8% of their birth weight
during the first few days of life. They regain this weight by the end
of the first 2 weeks. After this period of time, newborns typically gain
about 1 ounce per day during the first 2 months, and 1 pound per month
after that. This weight gain typically results in a doubling of birth
weight by age 5 months and a tripling by 1 year. In recent years, more
children have developed obesity. Some children become obese at an early age.
Weight and Length Charts for Infants from Birth to 24 Months of Age
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During the first year of life, an infant's weight and length are
charted at each doctor's visit to make sure that growth is proceeding at
a steady rate. Percentiles are a way of comparing infants of the same
age. For an infant at the 10th percentile for weight, 10% of infants
weigh less and 90% weigh more. For an infant at the 90th percentile, 90%
of infants weigh less and 10% weigh more. For an infant at the 50th
percentile, 50% of infants weigh less and 50% weigh more. Of more
significance than the actual percentile is any significant change in
percentile between doctor's visits. (Adapted from WHO Child Growth
Standards. Available at www.cdc.gov/growthcharts.)
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Height and Weight Charts for Boys and Girls 2 to 10 Years of Age
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Adapted from The National Center for Health Statistics in
collaboration with the National Center for Chronic Disease Prevention
and Health Promotion (2000). Available at www.cdc.gov/growthcharts.
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Head Circumference
Head circumference is measurement around the largest area of a
child's head. Doctors place the tape measure above the eyebrows and ears
and around the back of the head. This measurement is important because
the size of the head reflects the size of the brain, and this
measurement lets doctors know whether the child's brain is growing at a
normal rate. Head circumference is routinely measured until children are
3 years old.
At birth, the brain is 25% of its future adult size, and head
circumference is about 14 inches (about 35 centimeters). By 1 year of
age, the brain is 75% of its adult size. By 3 years of age, the brain is
80% of its adult size. By 7 years of age, the brain is 90% of its adult
size.
Teeth
The timing of tooth eruption varies, mainly for hereditary
reasons. However, tooth eruption may also be delayed by disorders such
as rickets, hypopituitarism, hypothyroidism, or Down syndrome.
Lower front teeth usually begin to appear by the age of 5 to 9
months. Upper front teeth usually begin to appear by 8 to 12 months. On
average, infants have 6 teeth by age 12 months, 12 teeth by 18 months,
16 teeth by 2 years, and all 20 of their baby (deciduous) teeth by 2½
years. Baby teeth are replaced by permanent (adult) teeth between the
ages of 5 years and 13 years. Permanent teeth tend to appear earlier in
girls.
More Information
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Growth charts from the World Health Organization (WHO)
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Growth charts from the Centers for Disease Control and Prevention (CDC)
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