Does the Bayley-III Motor Scale at 2 years predict motor outcome at 4 years in very preterm children?

Aim To assess the predictive validity of the Bayley Scales of Infant and Toddler Development Third Edition (Bayley-III) for later motor outcome. Method Ninety-six infants (49 males, 47 females) born at less than 30weeks' gestation admitted to two tertiary hospitals in Melbourne, Australia, were assessed with the Bayley-III Motor Scale at 2years' corrected age and were classified as suspect or definite motor impairment if they scored less than 1 or 2 standard deviations respectively, relative to the test mean. At 4years' corrected age, children completed Movement Assessment Battery for Children Second Edition (MABC-2); for the total motor score, cut-offs of not more than the 15th were used to classify motor development and cut-offs of not more than the 15th centile were classified as having a significant movement difficulty. Results Of the 96 children assessed at both ages, at 2years 9% had suspect and 4% had definite motor impairment; however, by 4years, rates had increased to 22% and 19% respectively. The specificity of the Bayley-III for motor impairments for later motor outcome was excellent (ranging from 94 to 100% for cerebral palsy [CP] and 97 to 100% for motor impairment), although the sensitivity was low (ranging from 67 to 83% for CP and 18 to 37% for motor impairment); many children with later impairment were not identified by the Bayley-III. Interpretation The Bayley-III Motor Scale at 2years underestimates later rates of motor impairment, particularly in the absence of CP at 4years on the MABC-2 total motor score in children born at less than 30weeks' gestational age.