Intelligence in Children of Very Low Birth Weight.

As there have been conflicting reports about intelligence in children of very low birth weight, advantage was taken of an opportunity to study the intelligence of 1,066 children weighing 4 lb. or less at birth who were the subjects of an investigation into the aetiology of cerebral palsy and other disorders* (McDonald, 1962, 1963). The many surveys of the intelligence of premature children were reviewed by Benton (1940) and more recently by Wiener (1962). In most studies premature children, who by definition have a birth weight of not more than 54 lb. (2,500 g.), have been found to have a lower mean I.Q. than heavier children. However, since socio-economic status is correlated with birth weight (Baird, 1962), and strongly correlated with performance in intelligence tests (Jones, 1954), it is by no means easy to ascertain whether there is an independent correlation between birth weight and intelligence. Benton (1940) concluded that, althougl the prevalence of mental defect was undoubtedly higher in premature than in heavier children, there was no evidence of any general intellectual inferiority among them. In particular, the careful survey by Mohr and Bartelme (1934) of the mental development of 250 children who had been admitted as infants to a premature baby unit supported this conclusion. Wiener (1962), on the other hand, considered that the evidence indicated that premature children were intellectually inferior to full-term children. He based this conclusion mainly on the surveys of Harper, Fischer, and Rider (1959) and Drillien (1961), in which, allowing for the effect of social factors, premature children were found to have lower mean