Patterns of cognitive development in very low birth weight children during the first six years of life

Background. Cognitive development in very low birth weight (VLBW, ≤1500 g) infants typically has been reported based on mean endpoints in cross- sectional studies. These overall group means mask individual patterns of cognitive development. Given the heterogeneity of VLBW infants, it is important to identify individual patterns of development and the factors associated with the different patterns. Objective. We sought to determine individual patterns of cognitive development over the first 6 years in VLBW children and to examine the relative influence of selected biomedical and sociodemographic factors on these patterns. Method. VLBW infants (N = 203) were followed from birth to six years. Cognitive scores were obtained at four yearly intervals, and biomedical and social data were obtained beginning with the neonatal period. Cluster analysis was used to identify individual patterns of cognitive development. Results. Five developmental patterns were identified: average-stable (13% of the sample); average-declined to low average (24% of the sample); average-declined to below average (43% of the sample); very low-increased to low average (8% of the sample); and very low- stable (12% of the sample). The patterns could be differentiated by several biomedical factors, including birth weight, gestational age, neonatal health, and 1-year assessments of neurological status and head circumference, as well as by level of maternal education. In particular, abnormal neurological status at 1 year was associated with a pattern of very low stable scores, and a suspicious status was associated with a pattern of improving cognitive development. Maternal education was influential among children born at the upper end of the VLBW range, who had a more favorable set of biomedical factors. Conclusions. Biomedical factors are of major importance for the cognitive development of VLBW infants, and their influence increases as birth weight declines. Differences in neurological integrity at 1 year were an important indicator of different patterns of cognitive development, especially for infants at the lower end of the VLBW range.