Influence of social background on psychomotor development in the first year of life and its correlation with later intellectual capacity: a prospective cohort study.

The effect of the sex of the child, somatic growth and five family background variables upon psychomotor development during the first year of life was studied by regression analysis in a Northern Finland birth cohort (n = 12 058) for 1966. Children with mental retardation and cerebral palsy were excluded from the series. The significant explanatory variables for the age of learning to stand and to walk without support were gestational age, birth weight, sex and maternal age. The girls and children of young mothers revealed a faster pattern of development. Urban residence enhanced learning to walk with support, an ability which was attained at the same age in both sexes. Female sex was the most powerful explanatory variable for early development of speech, the other significant variable being height at one year, birth weight, low parity of the mother and urban place of the residence. The social class and marital status of the mother proved insignificant for the developmental milestones studied here. The fast learners during their first year of life were superior to the others in their educational capacity at the age of 14 years. The prognosis in this respect was independent of social class.