The causes of cerebral palsy. Recent evidence.

Cerebral palsy (CP), unlike many other neurodevelopmental disorders, is associated with abnormalities of pregnancy and birth, particularly 'birth asphyxia' and low birthweight. Associations, however, need not be causal, and some prenatally damaged infants manifest clinical signs suggestive of birth asphyxia in the perinatal period. The lack of a clinically reliable indicator of impaired fetal-placental gas exchange limits our confidence that birth asphyxia plays a true causal role in cerebral palsy. Premature delivery is the single most important antecedent of cerebral palsy, and the increase in survival of very small infants resulting from newborn intensive care may augment this contribution in the future. Cranial ultrasound imaging can describe patterns of neonatal brain damage in the low birthweight infant that are highly predictive of later cerebral palsy. Future research on the causes of cerebral palsy may benefit from improvements in the neurological assessment of the fetus prior to labor and from a clearer understanding of the role of endocrine factors, particularly thyroid disorders, in neurologic development.