The Effects of Birth Inputs on Birthweight

Unobserved heterogeneity among childbearing women makes it difficult to isolate the causal effects of smoking and prenatal care on birth outcomes (such as birthweight). Whether a mother smokes, for instance, is likely to be correlated with unobserved characteristics of the mother. This article controls for such unobserved heterogeneity by using state-level panel data on maternally linked births. A quantile-estimation approach, motivated by a correlated random-effects model, is used to estimate the effects of smoking and other observables (number of prenatal-care visits, years of education, and so on) on the entire birthweight distribution.