Relationships of biological and environmental factors to cognition of preterm infants in the toddler and preschool periods.

One hundred and nine preterm infants were studied to examine the relative effects of biologic/neurologic factors (length of hospital stay, 18 month cognitive status) and environment (socioeconomic status) on cognition in the toddler (18 months) and preschool periods (3 years). Length of hospital stay was significantly related to toddler cognitive outcome, and less so to preschool outcome. Socioeconomic status predicted only preschool cognitive outcome and not toddler outcome. Cognitive status at 18 months significantly predicted 3 year outcome, and there was relatively little change between those periods. Together, cognitive status at 18 months and socioeconomic status significantly predicted preschool IQ, accounting for 34% of the variance. Results showed that perinatal biologic risks became less salient while socioeconomic status became increasingly important at the preschool period. Relative lack of change in cognitive status indicated the importance of early cognitive evaluation in preterm infants.