ABSTRACT
The terms trend and cerebral palsy are defined emphazing the non-diagnostic nature of the cerebral palsy label. Criteria necessary for valid estimation of trends include constant methods of estimating population based numerators and denominators over a number of years, which render them hard to obtain, particularly in developing countries. Trends in cerebral palsy are an important source of aetiological hypotheses for congenital cerebral palsy, provide corroborative evidence for existing hypotheses and may direct strategies to prevent post neonatally acquired cerebral palsy. In developed countries the overall frequency of congenital cerebral palsy has changed little during the last decades. However this masks a dramatic increase in the frequency in the infants born most preterm, a decline in those born moderately preterm and little change in those born at term, but the severity of impairments of those born very preterm is decreasing while for those born at term severity in increasing. These changes may be the result of the increasing ability of perinatal care to rescue very vulnerable infants. There is less agreement in trends of post neonatally acquired cerebral palsy which are more sensitive to social well being.