It has been thought that when the cause of the mental retardation and cerebral palsy is a period of lack of oxygen, newborns will show signs of brain damage immediately following birth called encephalopathy. The signs of encephalopathy can be seizures, abnormalities of muscle tone, abnormal movements and/or an abnormal mental state. It has also been assumed that newborns who require resuscitation at birth but are free of encephalopathy will have normal growth and development.