WORKING PAPER NO. 68 What All Women (and Some Men) Want to Know: Does Maternal Age Affect Infant Health?

The incidence of many commonly-studied birth outcomes, such as infant mortality and prematurity, varies by maternal age. In particular, both older and younger women face an increased probability of an unfavorable birth outcome. Whether this association is causal is an open question, as a mother’s age is correlated with other determinants of infant health, such as socioeconomic and marital status. If age does directly affect infant health, then delays in childbearing, as have occurred during the past thirty years, could have important implications for health outcomes and costs. In this paper I examine the relationship between maternal age and infant health. To control for unobservable differences across mothers, I create a unique large-scale panel data set of over one million sibling births from the universe of births in Texas between 1989 and 2001. Comparing outcomes across siblings using a generalized correlated random-effects model, I find that both younger and older mothers give birth to infants who are less healthy along several dimensions. Women over age 35 and under age 18 are 30 percent more likely to have a preterm delivery when compared to women between the ages of 26 and 29. Women giving birth at older ages also face elevated risks of infant death and of having a child with a