The CPP, originally called the National Collaborative Perinatal Project (NCPP), was launched in January 1959 and was a prospective cohort study of pregnancy and child health designed to identify determinants of cerebral palsy and allied neurological defects. Pregnant women were enrolled usually at their first prenatal visit between 1959 and 1966 at 12 hospitals across the United States. In total, approximately 49,400 pregnancies were included in the study. The mother was examined during pregnancy, labour, and delivery. The children were given neonatal examinations and follow-up examinations at four, eight, and twelve months, and three, four, seven, and eight years.