Developmental risks and protective factors for influencing cognitive outcome at 5 1/2 years of age in very-low-birthweight children.

In a population-based follow-up study (the Stockholm Neonatal Project), 182 children with a birthweight of 1500 g or less (very-low birthweight: VLBW) and a control group of 125 children born healthy at term were examined with the Wechsler Preschool and Primary Scale of Intelligence-Revised (WPPSI-R) and a neuropsychological test battery (Nepsy) at 5 1/2 years of age. The WPPSI-R results of the VLBW children fell well within the normal range: WPPSI-R full-scale IQ 95.7, verbal subscale IQ 99.9, and performance subscale IQ 91.6. Nevertheless, the control group had significantly better results than the VLBW group which could be attributed to the greater variability of the VLBW group, with a larger proportion falling in the lower area of the IQ distribution, especially on the performance subscale. Likewise, the control group displayed better executive function (Nepsy). Paternal education was equal in the two groups and was the single most important predictor of IQ, possibly acting as a protective factor. The need for glasses or lenses was inversely associated with all IQ measures and severe retinopathy of prematurity (ROP) had the most negative impact on full-scale and performance IQ. These two IQ measures were also negatively associated with intrauterine growth retardation late in pregnancy. We conclude that VLBW children, in the absence of these identified risk factors, have normal cognitive development.