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Child development is a dynamic interaction of biologic and environmental
factors. Typically, over a period of many years, an infant who is
initially entirely dependent on others to meet life-sustaining needs such
as food and shelter develops into an independent adult capable of
caring for others. Growth of a child’s skills occurs across
multiple domains of development, including motor, language, cognitive,
and socioemotional domains, and allows for slowly increasing independence.
Within any single domain, the sequence of new skills acquired is
fairly consistent, but there is significant individual variability
in the rate of development within and across the different domains
that complicates attempts to distinguish children with normal variations
in development from children with developmental delays. However,
early detection of developmental delays is essential to promote
early intervention that can improve developmental outcomes and family
adjustment. During well-child care, clinicians are the professionals
most likely to interact with a child early in development and thus
have a unique opportunity and responsibility to detect children
with developmental delays. The approach to the evaluation of developmental delay
is discussed further in Chapters 185 and 547.
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The sequences in which children gain new skills in motor, language,
cognitive, and socioemotional development are precisely delineated,
and for many skills, the age at which 50% of children will
be able to accomplish a specific task is known. A child’s developmental
age is defined as the age at which approximately 50% of
children would demonstrate similar functioning. Since developmental
age is determined on the basis of the child’s functioning,
it could be higher or lower than the chronological age.
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A global developmental delay occurs when a child’s
developmental age lags behind chronological age across all the domains
of development. The degree of delay is often quantified by calculating
the developmental quotient (DQ = developmental age/chronological
age × 100). When a child is developing
at the expected rate, the DQ is 100. However, if a 2-year-old child
is functioning at a 1-year-old developmental age, the child’s DQ
is 50, indicating that the child is developing at half the expected
rate. A DQ less than 75 to 80 represents a significant developmental delay.
When skills in one domain lag behind (or are more advanced than)
skills in other domains, a dissociation in the
domains of development occurs, such as seen with language disorders,
coordination disorders, and learning disabilities.
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Typically, a child’s developmental age is similar across
the different domains of development. However, when skills in 1
domain lag behind (or are more advanced than) skills in other domains,
a dissociation in the domains of development occurs.
Disassociations occur in situations such as language disorders,
coordination disorders, and learning disabilities.
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Intellectual disability (formerly mental retardation)
is defined as a significant deficit in both cognitive skills and
adaptive functioning that develops prior to 18 years of age.1 The deficit
in cognitive skills is determined by the intelligence quotient (IQ)
on a standardized IQ ...