The aim of this review is to determine the relationship between gestational age (GA) and prevalence, type, distribution, and severity of cerebral palsy (CP). Epidemiological studies with cohorts expressed by GA were assessed. A comprehensive meta-analysis and meta-regression was performed on four fetal age categories. Studies of children with CP as a target population were added. Twenty-six articles met the inclusion criteria. The prevalence of CP decreases significantly with increasing GA category: 14.6% at 22 to 27 weeks' gestation, 6.2% at 28 to 31 weeks, 0.7% at 32 to 36 weeks, and 0.1% in term infants. Interestingly, a significant decrease in prevalence of CP starts only from a GA of 27 weeks onwards. In preterm infants, spastic CP is predominant. In term infants, the non-spastic form of CP is more prevalent than in preterm infants. Bilateral spastic CP is most prevalent in both preterm and term infants. However, the proportion of unilateral spastic CP in term infants is substantial. No relationship could be detected between severity of CP and GA. There is a strong need for an international, well-described, and generally accepted classification system for subtypes and severity of CP.
