Objective: Our purpose was to determine the influence of being small for gestational age at term and being preterm < 34 weeks on cognitive functioning at age 5 years.
Study design: Five hundred forty-six children of black low-income mothers, nearly all at risk for being small for gestational age, followed up prenatally with early ultrasonographic gestational age dating, were classified as either term appropriate for gestational age, term small for gestational age, or preterm at < 34 weeks. At a mean of 5.5 +/- 0.5 years, a Wechsler Preschool and Primary Scale of Intelligence-Revised intelligence quotient test was administered. An intelligence quotient < 70 was used to define mental retardation. Univariate and multivariate analyses adjusted for maternal age, smoking, education and language skills, home environment, and child gender and preschool attendance were performed.
Results: Term small-for-gestational-age and preterm infants at < 34 weeks had 4 and 6 point intelligence quotient reductions compared with term appropriate-for-gestational-age infants. In the regression analyses these differences in intelligence quotient remained significant after confounders were adjusted. High maternal receptive language level (8 points), a positive home environment (5 points), and attendance at preschool (5 points) were each significantly associated with an increase in intelligence quotient.
Conclusion: Both term small-for-gestational-age infants and those born at < 34 weeks had a significantly lower mean intelligence quotient, and small-for-gestational-age infants had an increased risk of mental retardation at age 5 years. Higher maternal language skills, a positive home environment, and attendance at preschool each were associated with an increase in the mean intelligence quotient of 5 to 7 points.