An individual with mental retardation (MR) is best characterized as having both low to below-average thinking and reasoning skills as measured by a standardized intelligence test, and a limited ability to function in areas of daily life including communication, self-care, and social and interpersonal skills. A diagnosis of MR also requires that the condition occur in the developmental years, prior to age 18.
MR has many different causes. In some instances injury, genetic/chromosomal abnormalities, or infection causes MR. These causes can occur before birth or during childhood (up to age 18).
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In most instances the cause of MR is unknown, but some of the most common causes that occur before birth are Down syndrome, Fetal Alcohol Syndrome (FAS), and Fragile X Syndrome. Other causes include genetic conditions such as Cri-du-chat Syndrome or Prader-Willi Syndrome, infections such as congenital cytomegalovirus, or birth defects that affect the brain like hydrocephalus or cortical atrophy. MR can also be the result of extreme lack of oxygen near the time of birth. MR may develop in an older child as the result of serious head injury, stroke, or infections such as meningitis.
Approximately 1% to 3% of children in the United States are estimated to have MR.
MR is not preventable in most cases. However, some metabolic conditions such as phenylketonuria (PKU), galactosemia, and congenital hypothyroidism can be treated before the onset of mental retardation. These conditions can be identified through a simple blood test or heel prick (to draw blood) after the baby is born. There are also tests during pregnancy to assess whether a baby has chromosomal abnormalities such as Down syndrome.
In the United States, newborns are screened for metabolic disorders soon after birth, but different states test for different conditions. Parents can request that their baby be checked for any conditions that have an available test. Children with metabolic conditions are usually treated with medicine or put on a special diet. If the treatment is started very soon after the child is born and continues as long as needed, the child will probably not develop MR. Fetal Alcohol Syndrome can also be prevented: pregnant women should not drink alcohol.
- MR is a developmental disability that occurs prior to age 18;
- MR is sometimes preventable, but when present, the child and family will have special needs that must be supported in order to maximize the child's development;
- if parents are concerned about their baby's mental growth and development they should speak with a healthcare professional;
- alcohol consumed by a pregnant woman can result in FAS and MR; and
- parents should request screening tests for their newborn babies.
Mary is a well-educated woman who decided to focus on her career before getting pregnant. Now 40 years old, Mary is pregnant with her first child. Wanting to do everything right, Mary receives routine prenatal care, and is told during a second trimester visit that her alpha-fetoprotein level is low, suggestive of Down syndrome. A follow-up amniocentesis is inconclusive, but Mary decides not to have any more tests. One week past her due date, Mary's water breaks and, after 18 hours of labor, she delivers the baby. The baby has features distinctive of Down syndrome, such as a small head that is flattened at the back, a flattened face with a recessed nose bridge, and upward slanted eyes with epicanthal folds at the inner corners. Mary's physician refers her to the hospital social worker who helps the parents understand their child's needs and suggests ways to promote the family's bonding and child's development.
- Page last reviewed: February 22, 2011
- Page last updated: February 22, 2011
- Content source:
- Centers for Disease Control and Prevention
- Page maintained by: Division of Public Affairs (DPA), Office of the Associate Director for Communication (OADC)