A number of persons are exempt from the accident and emergency charge, including medical card holders, women receiving services in respect of motherhood, children up to the age of six weeks and children referred for treatment from child health clinics and school health examinations. Also exempt from these charges in respect of treatment for the particular condition are children suffering from prescribed diseases, that is, mental handicap, mental illness, phenylketonuria, cystic fibrosis, spina bifida, hydrocephalus, haemophilia and cerebral palsy. Where exemptions do not apply, the charge may be waived if, in the opinion of the chief executive of the appropriate health board, payment would cause undue hardship.