Mental performance of very low birth weight preterm infants: assessment of stability in the first two years of life and factors associated with mental performance.

The aim of this study was to investigate the stability of mental performance of very low birth weight premature infants during the first two years of life, and to identify factors associated with mental performance.The study included 109 children. The Mental Scale of Bayley Scales of Infant Development - Second Edition was administered at 6, 12 and 18-24 months of corrected age. The stability of the scores between assessments was verified by the analysis of variance for repeated measures.The association of the major social and neonatal characteristics with mental development was confirmed using multivariate analysis by linear regression, considering the following outcomes: mental development indices at 6 months, 12 months and between 18-24 months of corrected age. The mean Mental Developmental Index (MDI) was 83.4 (SD: 12.4) at 6 months, 86.4 (SD: 13.9) at 12 months, and 73.4 (SD: 14.5) at 18-24 months. A significant decrease in the mental developmental index (13 points) at 18-24 month corrected age was observed. The Mental development index did not show stability during the first two years of life in this population of preterm infants, except for children with neonatal pneumonia whose performance was unsatisfactory in all assessments. Among the risk factors investigated only male gender and neonatal pneumonia were associated with outcomes.