this is true or not :) mental retardation is one of the factors affecting the evolution of language development. #mental retardation are classified into nine groups. noted that some of these reasons may occur before birth, during birth and some others after birth, and these reasons include. *Infection & Intoxication: Maternal infections during pregnancy * Cross Brain Diseases: Brain tumors. * Trauma or Physical Agents: Head injuries as a result of accidents or falls from high places * unknown Prenatal Influences: Introduces including genetic factors and health status of the mother during pregnancy * metabolic or Nutrition: One of these disorders is known as the status of PKU, as that malnourished pregnant and the baby of the factors that may affect * Sensory Impairment : Included among these injuries visual and auditory difficulties may lead to such extreme deprivation in experience * Psychiatric Disorder: * Environmental Influences: a combination of factors related to the cultural and economic status of the family * chromosomal Abnormality: refers to a bug that exposed the process of a fertilized egg splits