Mental retardation is a term used when a person has certain limitations in mental functioning and in skills such as communicating, taking care of him or herself, and social skills. These limitations will cause a child to learn and develop more slowly than a typical child. Children with mental retardation may take longer to learn to speak, walk, and take care of their personal needs such as dressing or eating. They are likely to have trouble learning in school. They will learn, but it will take them longer. There may be some things they cannot learn. The most common causes of mental retardation are: 1). Genetic conditions. Sometimes mental retardation is caused by abnormal genes inherited from parents, errors when genes combine, or other reasons. Examples of genetic conditions are Down syndrome, fragile X syndrome, and phenylketonuria (PKU). 2). Problems during pregnancy. Mental retardation can result when the baby does not develop inside the mother properly. For example, there may be a problem with the way the baby's cells divide as it grows. A woman who drinks alcohol or gets an infection like rubella during pregnancy may also have a baby with mental retardation. 3) Problems at birth. If a baby has problems during labour and birth, such as not getting enough oxygen, he or she may have mental retardation. 4. Health problems. Diseases like whooping cough, the measles, or meningitis can cause mental retardation. Mental retardation can also be caused by extreme malnutrition (not eating right), not getting enough medical care, or by being exposed to poisons like lead or mercury. This book presents new and important research in the field.