Cognitive and neurologic development of the premature, small for gestational age infant through age 6: comparison by birth weight and gestational age.

OBJECTIVE: To compare the neurologic and cognitive outcomes of 129 premature small for gestational age (SGA) infants with 300 premature appropriate for gestational age (AGA) infants through 6 years of age.

DESIGN: Infants born at < or = 37 weeks gestational age and < or = 2500 g with birth weight 2 standard deviations or more below the mean birth weight for gestational age were categorized as SGA. Cognitive and neurologic outcomes of SGA and AGA prematures at 1, 2, 3, and 5 and/or 6 years of age were compared when the infants were stratified by gestational age in 2-week intervals or by birth weight in 500-g intervals. The association between SGA/AGA and neurologic status on cognitive outcomes at each age was also examined.

RESULTS: SGA infants had significantly poorer cognitive scores at each age when compared with AGA infants of similar gestational ages. Normal neurologic status was more likely at all assessments for the AGA than for SGA infants of comparable gestational age. There were no differences between SGA and AGA children in cognitive or neurologic outcomes at any age when grouped by birth weight. Cognitive impairment was closely associated with neurologic abnormality in both SGA and AGA groups. There was, nevertheless, a significant effect of SGA on cognitive outcome independent of neurologic status at all ages except 3 years.

CONCLUSIONS: Irrespective of degree of prematurity, SGA infants are at greater risk for neurodevelopmental impairment than are equally premature AGA infants. The cognitive impairment can be largely, but not entirely, attributed to a higher incidence of neurologic abnormalities in the SGA infants at each gestational age.