Evaluating the impact of poverty-reduction programs on fertility is complicated given that changes in incentives to have children take time to be incorporated into decision making and evaluation periods are usually quite brief. We explore the use of birth spacing as a short-run indicator of the impact of poverty-reduction programs on fertility. The data come from a Nicaraguan conditional cash transfer program that offers incentives for poor households to invest in children’s health, nutrition, and education. We estimate a stratified Cox proportional hazard model and find that the program decreased the hazard of a birth, indicating an increase in birth spacing.