Accuracy of the Bayley-II Mental Development Index at 2 Years as a Predictor of Cognitive Impairment at School Age among Children Born Extremely Preterm

OBJECTIVE: To describe the accuracy of the Bayley Scales of Infant Development-Second Edition (BSID-II) Mental Development Index (MDI) at 2 years of age for prediction of cognitive function at school age of children born extremely preterm. DESIGN: Study participants were enrolled in the Extremely Low Gestational Age Newborn Study between 2002 and 2004. Two-thirds of surviving children (n=795) were assessed at 2 years with the BSID-II and at 10 years with an intelligence quotient (IQ) test. We computed test characteristics for a low MDI (< 70), including predictive value positive. RESULTS: Almost two-thirds of children with a low MDI had a normal IQ (≥ 70) at 10 years. Concordance between MDI and IQ was highest among children with major motor and/or sensory impairment, and when MDI was adjusted for gestational age. CONCLUSION: Most children born extremely preterm with low BSID-II MDI at 2 years have normal intelligence at school age.