['To examine adverse birth events on the development of cerebral palsy in California.', 'A retrospective population-based study of children with cerebral palsy (as of Nov. 30, 2006), matched to their maternal/infant delivery records (Jan. 1, 1991 to Dec. 31, 2001) was performed. Demographic data and intrapartum events were examined. Six adverse birth-related events were chosen. Children without cerebral palsy were controls.', 'There were 7242 children who had cerebral palsy (59% term) and 31.3% had 1 or more of the 6 adverse intrapartum events (12.9% in controls P < .0001). This held for both term (28.3% vs 12.7% controls) and preterm (36.8% vs 15.9%, controls) neonates (both P < .0001). Maternal (15.1% vs 6.6%) and neonatal (0.9% vs 0.1%) infection were increased in cerebral palsy cases (P < .0001).'] Are adverse obstetric events associated with significant risk of cerebral palsy?