Early spontaneous movements assessed by the Motor Optimality Score-Revised are associated with social referencing at 18 months in a community-based population.

OBJECTIVE: Early spontaneous motor movements are important indicators of neurodevelopment. The Motor Optimality Score-Revised (MOS-R) is a detailed assessment of general movements during early infancy however, its association with later developmental characteristics in community-based populations remains unclear. We explored the association between the MOS-R at 10-19 weeks' corrected age and Modified Checklist for Autism in Toddlers, Japanese Version (M-CHAT-JV) outcomes at approximately 18 months of age. METHODS: This prospective observational study included infants born at term who attended routine 4-month health checkups in two rural cities in Japan. The MOS-R was assessed by a certified evaluator. The M-CHAT-JV was administered at approximately 18 months of age. Associations between the MOS-R subcategories and the M-CHAT-JV subdomains were explored. For infants assessed at ≥16 weeks' corrected age, hand-to-hand contact, foot-to-foot contact, and legs lift were additionally analyzed. RESULTS: Sixty-six infants were analyzed. The median MOS-R total score was 26, and 22.7% of infants had reduced scores (<25). The observed postural patterns were associated with social referencing on the M-CHAT-JV (p = 0.018). Among infants assessed at ≥16 weeks, the absence of normal legs lift was associated with poorer social-referencing outcomes (p = 0.048). No significant associations were identified between fidgety movements and other MOS-R subcategories. CONCLUSIONS: Legs lift may be associated with social referencing at approximately 18 months of age in this community-based cohort. A preliminary association was also suggested between observed postural patterns and social referencing. These exploratory findings require confirmation in larger, independent studies.