Correction for prematurity and its consequences for the assessment of the very low birth weight infant.

The consequences of correcting developmental test scores for the degree of prematurity were studied in 2 cohorts of children each composed of demographically matched groups of preterm and full-term infants. The children were administered the Bayley Scales at 4, 8, 12, 18, and 24 months of age; the Stanford-Binet at 3 years; the Reynell Developmental Language Scales at 2, 3, and 4 years; and the McCarthy Scale of Children's Abilities, the ITPA Grammatic Closure, the Northwestern Syntax Screening Test, the Beery Developmental Test of Visual Motor Integration, and the Peabody Picture Vocabulary Test at 5 years. At each point in time, except some language measures at 5 years, the uncorrected scores of the preterms were significantly lower than those of the full-terms. Although the corrected scores were significantly lower early in development, they were not lower at 5 years, with the exception of the Beery VMI, a measure of perceptual-motor skills. In the first year the corrected scores were typically more highly correlated with 3-year and 5-year test scores. From 12 months on the uncorrected scores were usually more highly correlated. The same pattern was evident for the prediction of developmental delay. Correction for degree of prematurity appears to be appropriate in the first few months. After that point, slightly more accurate prediction is achieved by using the uncorrected scores. Early test scores are significantly influenced by the degree of biological maturity, but the impact of environmental influences increases with development.