Gross motor milestones in preterm infants: correction for degree of prematurity

The age of gross motor milestone attainment and how it is affected by degree of prematurity at delivery were studied in 100 high-risk, preterm (less than 32 weeks) infants with normal motor outcome. We calculated the mean age of attainment for each milestone on the basis of chronologic age from the date of delivery and term age equivalent, correcting for degree of preterm delivery. Half of these preterm infants were male; 70% were black. The infants were compared with a population of normal infants born at term. In this very preterm population, there were no consistent sex differences, but black infants generally attained motor milestones before white infants. For each motor milestone, regardless of gender or race, the mean term age equivalents of attainment for very preterm infants closely approximated the mean ages of milestone attainment for term infants, whereas the mean chronologic ages were delayed 2 or 3 months. We conclude that very preterm infants can be expected to demonstrate sequential gross motor development at a rate expected for degree of prematurity. Chronologic age is not a valid measurement scale to use in determining motor delay in very preterm infants.