Stability of Cognitive Outcome From 2 to 5 Years of Age in Very Low Birth Weight Children

Abstract

This study assessed the stability of cognitive outcomes of premature, very low birth weight (VLBW; ≤1500 g) children. A regional cohort of 120 VLBW children born between 2001 and 2004 was followed up by using the Bayley Scales of Infant Development, Second Edition, at 2 years of corrected age and the Wechsler Preschool and Primary Scale of Intelligence-Revised at the age of 5 years. The Mental Development Index (MDI) and the full-scale IQ (FSIQ) were measured, respectively. A total of 168 randomly selected healthy term control children born in the same hospital were assessed for MDI and FSIQ. In the VLBW group, mean ± SD MDI was 101.2 ± 16.3 (range: 50-128), mean FSIQ was 99.3 ± 17.7 (range: 39-132), and the correlation between MDI and FSIQ was 0.563 (P < .0001). In the term group, mean MDI was 109.8 ± 11.7 (range: 54-128), mean FSIQ was 111.7 ± 14.5 (range: 73-150), and the correlation between MDI and FSIQ was 0.400 (P < .0001). Overall, 83% of those VLBW children who had significant delay (-2 SD or less) according to MDI had it also in FSIQ. Similarly, 87% of those children who were in the average range in MDI were within the average range in FSIQ as well. Good stability of cognitive development over time was found in VLBW children and in term children between the ages of 2 and 5 years. This conclusion stresses the value and clinical significance of early assessment at 2 years of corrected age. However, we also emphasize the importance of a long-term follow-up covering a detailed neuropsychological profile of these at-risk children.