Causative factors in cerebral palsy (CP) vary to some degree according to gestational age group and clinical CP subtype. Such catastrophes of birth as placental abruption, cord prolapse, and uterine rupture sharply heighten risk of CP. These conditions are fortunately uncommon, and are sometimes not survived; individually and collectively they account for only a small proportion of CP. Among other factors associated with increased risk of CP are prematurity, intrauterine exposure to infection or maternal fever in labor, ischemic stroke, congenital malformations, atypical intrauterine growth (restricted or excessive for gestational age), and complications of multiple gestations. Although any 1 factor, if severe, may be sufficient to cause CP, more often it is the presence of multiple risk factors that overwhelms defense mechanisms and leads to CP. The contribution of genetic vulnerabilities that interact with environmental stressors is an emerging aspect of our understanding of causative factors in CP.