Born Small for Gestational Age and Poor School Performance – How Small Is Too Small?

Abstract

Aim: To assess the relationship between severity of small for gestational age (SGA) and the risk of poor school performance, and to investigate whether adult stature modifies this risk. Methods: 1,088,980 Swedish children born at term between 1973 and 1988 were categorized into severe SGA (less than –3 standard deviations (SD) of expected birth weight), moderate SGA (–2.01 to –3 SD), mild SGA (–1.01 to –2 SD), and appropriate for gestational age (–1 to 0.99 SD). The risk of poor school performance at the time of graduation from compulsory school (grades <10th percentile) was calculated using unconditional logistic regression models and adjusted for socio-economic factors. In a sub-analysis, we stratified boys by adult stature, and adjusted for maternal but not paternal height. Results: All SGA groups were significantly associated with an increased risk of poor school performance, with adjusted odds ratios and 95% confidence intervals ranging from 1.85 (1.65–2.07) for severe SGA to 1.25 (1.22–1.28) for mild SGA. In the sub-analysis, all birth weight groups were associated with an increased risk of poor school performance among boys with short stature compared to those with non-short stature. Conclusion: Mild SGA is associated with a significantly increased risk of poor school performance, and the risk increases with severity of SGA. Further, this risk diminishes after adequate catch-up growth.