Developmental delay is the term used to describe a child's significant lag behind peers in physical, communication, social, or cognitive skills. Often the emphasis is on cognitive ability or a combination of skills.
In some states, every child with a special need is said to have a developmental delay until age six, regardless of an obvious condition such as blindness, deafness, or cerebral palsy. The rationale is that other disabilities may also be present, and singling out an area of need too early may cause something to be overlooked. By age six, professionals have a more thorough understanding of how the child functions in all areas.
Illness, injury, complications at birth, genetics, and unknown factors can result in developmental delay in a specific area (such as cognitive skills like mental retardation) or delay in a combination of areas.
Down syndrome is one of the most common examples of developmental delay. This condition is the result of an unusual chromosome split; a child with Down syndrome has 47 chromosomes instead of 46.
The physical characteristics of a child with Down syndrome include slanted eyes, somewhat flattened face, one crease across the palm of the hand, and low muscle tone. A child with Down syndrome is more likely to have medical problems, including hearing, vision, thyroid, heart, and general infections. As far as behavior, a child with Down syndrome may characteristically be loving and yet very stubborn.