Sources of variability in sequelae of very low birth weight.

Few investigations have examined the specificity of sequelae of very low birth weight (VLBW, <1500 g) or sources of variability in outcome. To better understand the nature and determinants of outcome, we assessed neuropsychological and achievement skills at mean age 11 years in 62 children with <750 g birth weight, 54 with 750-1499 g birth weight, and 66 term-born controls. Distinct cognitive constructs were identified by factor analysis, and the three birthweight groups were compared on these constructs and on composite measures of achievement. Although the group with <750 g birth weight performed less well on all tests than term-born controls, group differences in a perceptual planning factor and in mathematics remained even when IQ was controlled, and deficits were more pronounced in mathematics than in reading. Results from structural equation modeling were consistent with the hypothesis that neuropsychological skills mediated the relationship between birth weight and achievement. The findings confirm the differential deficit hypothesis, support the need to consider multiple sources of variability in VLBW outcomes, and highlight the importance of neuropsychological constructs in developing an explanatory framework.