Aim  The aim of this study was to assess overall and gestational age-specific trends in the rate of cerebral palsy (CP) in Victoria, Australia, and to compare these findings with other population data.

Method  Individuals born in Victoria from 1970 to 2004 with non-postneonatally acquired CP were identified from a population register; 3491 were included in the study (1963 males, 1528 females). After a literature review, comparison data were extracted from publications using previously devised inclusion criteria. Rates were calculated per 1000 live births for all CP and by gestational age group: these were tabulated and plotted by year of birth.

Results  Data from nine registries, including the Victorian register, showed an increase in the rates of CP over the 1970s and 1980s, consistently seen in extremely preterm (<28wks) survivors but also in those born at term (≥37wks). Since the early 1990s, CP rates either stabilized or decreased, particularly for children born extremely preterm.

Interpretation  Increases in the rates of CP during the 1970s and 1980s are in part because of the increasing survival of extremely preterm infants that occurred without a concomitant improvement in neurological outcomes. Evidence from population samples now suggests that this trend has been reversed since the mid- to late 1990s.