Small-for-Gestational-Age and Vocabulary and Achievement Test Scores at Age 9 Among Children Born at Term in a Contemporary U.S. Sample

Introduction Children that are small-for-gestational-age (SGA) at birth are at an increased risk for cognitive impairment, even if born at term (37–41 weeks). This study examined associations between sex-specific SGA and vocabulary and achievement tests in 9 year old children born at term using a contemporary population-based US sample. Methods A secondary data analysis was conducted on a sample of 2144 children born at term in 1998–2000 who participated in a US birth cohort study that oversampled non-marital births, which in the U.S. are associated with socioeconomic disadvantage and racial minority status. Vocabulary and achievement tests were administered to participants at age 9. Unadjusted and adjusted Ordinary Least Squares and logistic regression models of associations between SGA and test scores were estimated. Results Sex-specific SGA was associated with 2–5 point lower test scores and 1–2 times the odds of scores less than 85 (> 1 SD below the national mean) across most outcomes. In adjusted models, measures of SGA were associated with low scores on the Woodcock–Johnson Applied Problems test (OR 2.257; 95% CI 1.434, 3.551) and the Woodcock–Johnson Passage Comprehension test (OR 1.554; 95% CI 1.132, 2.134). Conclusion The findings validate previous studies of SGA at term and cognitive outcomes and provide further evidence using a contemporary high-risk population-based US sample. The findings suggest that SGA children born at term should be recruited for early interventions to promote improved cognitive functioning in school. Significance This study expands and updates the relatively small literature on SGA and developmental outcomes among children born at term. This was done by estimating associations between sex-specific SGA status and vocabulary and achievement tests of 9-year-old children born at term who were part of a national US birth cohort study. The cohort study over-sampled non-marital births, which in the United States are associated with socioeconomic disadvantage and racial minority status.