Association between small-for-gestational age and poor school performance in 2 500 000 children born 1973–2002

Aim: To examine the association between infant weight for gestational age and school performance when leaving school at 16 years of age. Methods: Out of 2 525 571 infants born near- or at term, between 1 January 1973 and 31 December 2002, identified from the Swedish Medical Birth Register, 65 912 (2.6%) were born small-for-gestational age (SGA). Outcomes studied were the risk for the need for education in special school, and the final average grades. Modified Poisson regression analyses and weighted linear regression analyses were performed. Results: An association between SGA and the need for a special school was found, irrespective of restrictions or adjustments (RR between 2.47 and 2.25). SGA was associated with final grades below the 10th and 25th percentile (RR 1.49 and 1.18, respectively). A linear relationship between maternal height and the RR for education in special school (p = 0.005), suggested that SGA is a stronger risk factor among children of tall than of shorter women. Conclusion: SGA increased the risk for poor school performance, and for the need for a special school. We found an association between maternal height and school performance in relation to birthweight, suggesting that maternal height should be considered when estimating the impact of SGA on later outcomes.