Abstract
This commentary reflects on a natural experiment reported by Casey et al. (Am J Epidemiol. 2018;187(8):1586-1594) that tested the association between living near a coal or oil power plant and preterm birth. They found that retiring power plants resulted in a significant reduction in preterm birth, with larger effects observed for late preterm birth and among non-Hispanic black mothers and infants. Natural experiments, in particular the Utah Valley Steel Mill closure, have played a prominent role in the evidence base for air pollution regulation due to their demonstrated impact on cardiopulmonary effects in adults. Reproductive health, including infant mortality and preterm birth associated with poor air quality, has generally received less attention. Even small reductions in preterm birth can have a large population health impact, both in terms of preventing mortality in the short-term an in preventing lifelong disability among affected infants.