Objective. Extremely low birth weight (ELBW) infants are at greater risk for neurodevelopmental delay than full-term infants. Outcomes may be compromised secondary to abnormal brain development associated with complications of prematurity. Long-term cognitive outcome has also been reported to be significantly influenced by postnatal factors. The objective of this study was to clarify the effects of prematurity separate from environmental factors on growth and neurodevelopmental outcomes by comparing ELBW children with their full-term siblings.

Methods. The study consisted of 25 ELBW children, a subset selected from a larger population of infants who were <801 g birth weight and enrolled in a longitudinal follow-up project from birth and their 25 full-term, full-weight siblings. Twenty-three sets of siblings were evaluated at 5 years of age and 2 sets at 3 years of age with standardized medical, social, cognitive, motor, and language testing. Physical and neurodevelopmental outcomes were compared between groups, controlling for gender and socioeconomic status (SES).

Results. At follow-up, ELBW children were lighter, were shorter, and had smaller head circumference. The ELBW children had lower Stanford-Binet IQs (85 ± 12 [mean ± SD] and 95 ± 11), with lower Stanford-Binet subtests except short-term memory and quantitative reasoning, lower spelling scores on the Wide Range Achievement Test, and lower Peabody motor quotients (79 ± 11 and 92 ± 17). Preschool Language Scale quotients were not different, but other receptive language measures were lower for ELBW children. High SES seemed to modify the impact of preterm status on cognitive and language but not motor scores. The mean IQ for high-SES ELBW children was equivalent to that of the low-SES term siblings.

Conclusions. Preschool-age cognitive and language functioning in ELBW children seemed to be affected by both prenatal and birth influences (preterm status) and postnatal influences (SES variables). Motor scores were significantly related to preterm status but not to SES.

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