Causal subgroups and declining rates of cerebral palsy in Victoria, Australia

AIM: To determine the extent to which specific patho-aetiological subgroups contributed to declines in prevalence of cerebral palsy (CP) observed in many high-income countries over this millennium. METHOD: This epidemiological study used data from the Victorian CP Register on 2303 children born in Victoria between 2000 and 2019. Joinpoint regression analysis was used to assess trends in birth cohort prevalence of CP per 100 000 live births for well-defined subgroups based on likely causal pathway, birth condition, and neonatal course. RESULTS: Linear rate decreases were seen for two subgroups: (1) children born before 35 weeks' gestation with perinatal insults (annual percent change -3.12 [95% confidence interval - 4.63, -1.58]) and (2) children born from 35 weeks with perinatal, non-focal hypoxic-ischaemic insults and encephalopathy (annual percent change -5.98 [95% confidence interval - 8.46, -3.44]). Evidence was lacking for sustained decreases in CP rates for subgroups of children with early developmental causes, perinatal arterial ischaemic strokes, predominant white matter injury patterns in association with birth from 35 weeks, and postneonatal causes. INTERPRETATION: The steepest declines in rates of CP in Victoria were for causal subgroups involving perinatal cerebral insults and significant neonatal complications, suggesting that advances in perinatal care may be driving the decreasing CP rates.