Infant motor development is a robust predictor of long-term developmental outcomes, especially in infants at high risk for neurodevelopmental impairments, such as those born preterm (PT, gestational age [GA] <37 weeks). Although direct assessments of motor development are available, they are infrequently applied by pediatricians in routine screening of the broader population of infants born preterm. Parent ratings, such as the Ages and Stages Questionnaire, 3rd Ed., can be used to screen for motor delays. However, this and other existing screening measures focus on whether children have reached milestones based on pre-established cutoffs, rather than on assessing development along a continuum of ability. The present study examined the validity of the Motor domain of the recently developed caregiver report screening tool, PediaTracTM, in distinguishing infants born PT from infants born full term (FT, GA ^37 weeks) across the first 6 months of life. The reliability and factor structure of this motor scale were also evaluated.

PediaTracTM is a web-based caregiver report assessing infant development across multiple domains, including motor functioning. This study reports on results from the PediaTracTM Motor domain for the study sample of 571 caregiver-infant dyads (240 PT, 331 FT). Caregivers rated their infants on age-targeted motor skills during the newborn period (NB, defined as term equivalent for the PT group) and at 2-, 4-, and 6-months after the NB period. Item Response Theory (IRT) methods were applied to assess the reliability (i.e., information) of caregiver-reported motor skills at each age. Using the IRT item parameters of discrimination and difficulty, items were selected for inclusion and to estimate theta, an index of the latent trait, motor ability, for each infant. Analyses conducted at each age assessed the effects of group, sex, and group x sex on the motor trait. Scale reliabilities and factor structure were also examined.

The PT group had significantly higher scores than the FT group on the motor trait at the NB period but significantly lower scores by 4 and 6 months, suggesting slower development of motor skills in the PT group. Means (SD) theta scores (similar to z scores) for the PT and FT groups, respectively, were .14 (.88) and -.05 (.91) for the NB period, -.01 (.90) and .01 (.91) for 2 months, .20 (.90) and .36 (88) for 4 months, and .46 (78) and .66 (.89) for 6 months. Effects for sex and group x sex interactions were not significant. Reliabilities, estimated at a point close to mean theta, were .94, .93, .96, and .98 at the NB, 2-, 4-, and 6-month periods, respectively. Exploratory factor analyses revealed evidence for a single primary motor factor and multiple second-order factors at each age.

Findings provide strong support for applications of the caregiver reported PediaTracTM motor scales in screening infants born PT and other at-risk populations for early delays or abnormalities in motor development. Advantages of this method include its ease of administration, sensitivity to developmental change, and promise in assessing subdomains of motor skill.