The Effect of Birthweight on Educational Achievement

Florencia Torche, New York University
Ghislaine Echevarria, Pontificia Universidad Católica de Chile

Uterine growth predicts health, developmental, and socioeconomic outcomes. The question about whether this relationship is causal or driven by unobserved characteristics of low-weight infants is, however, still open. By linking birth records to standardized test scores for all 4th graders in Chile, and using twin fixed effects, we examine the causal effect of fetal growth on early educational achievement in a developing country. Birthweight differences within twin pairs have a substantial effect on test scores, with a 400-gram increase in birthweight resulting in a 15% standard deviation-gain in Math scores. The effect is larger among monozygotic than dizygotic pairs, reaching more than 20% s.d. The effect varies across family socioeconomic status. It is strongest among low-SES families but disappears among high-SES ones, suggesting that socioeconomic resources fully compensate for early disadvantage. Findings are particularly relevant in the developing world, where fetal growth restriction is the main determinant of low birthweight.