Corrected and uncorrected Bayley scores: Longitudinal developmental patterns in low and high birth weight preterm infants

In this study, we longitudinally investigated developmental changes in very low birth weight (VLBW, less than 1500 gms), in higher birth weight (HBW, 1500–2000 gms) preterm, and in full-term (FT) infants. We also investigated changes in their caretaking home environment. The subjects were 20 VLBW, 39 HBW, and 24 FT infants who participated in an intervention study. Blind independent assessments were performed at 4, 8, 12, and 16 months corrected age using the Bayley mental and motor scales, both corrected for prematurity and uncorrected, the Infant and Toddler temperament questionnaires, and the Caldwell Home Observation for Measurement of the Environment inventory (HOME). The VLBW infants obtained the lowest mental (77) and motor (77) uncorrected scores, which were significantly different from the mental and motor scores of the HBW (94 and 89, respectively) and of the FT (115 and 109, respectively) infants. Mental and motor uncorrected scores were significantly lower at 4 months than at 8, 12, and 16 months. By 12 months, the uncorrected scores of the HBW infants no longer differed from the FT ones, and by 16 months only the difference between the FT and the VLBW was significant. The corrected mental and motor scores yielded no significant group or age differences. Post hoc analysis of an interaction in the motor scores yielded significantly higher scores for the FT than for the VLBW group at the last assessment. Overall, the VLBW infants were more passive and less intense than were either HBW or FT infants. In general, the home environment of the VLBW infants was significantly less stimulating and responsive than was the home environment of the FT and HBW infants. These results are discussed in terms of vulnerability of the VLBW preterm infants to developmental deficits and the difficulties their parents experience in their caretaking role.