Use of chronological and adjusted ages to compare motor development of healthy preterm and fullterm infants.

To investigate the influence of gestational age at birth on motor development in infancy and the practice of basing motor assessments of preterm infants on an adjusted age, 21 healthy preterm and 23 fullterm infants were administered the Peabody Developmental Motor Scales at 12, 15 and 18 months of age. When quotients were based on chronological age, both the mean gross-motor and fine-motor developmental quotients of the fullterm group were significantly higher than those of the preterm group, indicating that the fullterm group had higher levels of motor development. However, when the quotients of the preterm group were based on adjusted age, which accounted for gestational age at birth, the motor quotients of the two groups did not differ significantly. It seems that motor development of healthy preterm and fullterm infants differs primarily as a function of gestational age at birth, which supports maturational theory and the practice of making age adjustments when evaluating motor development of preterm infants.