The aim of this study was to determine the best cut-off score for determining motor delay in the Motor Scale of the Bayley Scales of Infant-Toddler Development-3rd Edition (Bayley-III) when compared to the Neuro-Sensory Motor Development Assessment (NSMDA) for low birth weight and preterm infants during the first year of life. One hundred and sixty infants born before 32 weeks of gestation and with birth weights of 1500 grams or less were included. Classifications of delay using different Bayley-III cut-offs were cross-tabulated with the NSMDA functional classification. Predictive values of sensitivity, specificity, positive predictive value, and negative predictive value were calculated with 95% CIs. The sensitivity of a Bayley-III cut-off < 85 was 100% at 1, 8, and 12 months and 92.3% at 4 months. The best score on the Bayley-III for identifying infants with mild/moderate/severe motor problems on the NSMDA was 80 (100% at 1, 4, and 8 months; 91.3% at 12 months). For identifying motor impairments using the Bayley-III in low birth weight and preterm infants at 1, 4, 8, and 12 months old, the proper cut-off scores are 80-85.

Keywords: Bayley-III, assessment, cut-off, infant, low birth