This article reviews the empirical literature on spontaneous quitting of cigarette smoking among pregnant women. We define spontaneous quitting and discuss its prevalence and the characteristics that differentiate spontaneous quitters from women who continue to smoke during pregnancy. We examine the success of these women in abstaining throughout their pregnancy, and their pattern of relapse back to smoking during the postpartum period. We review studies that have tested strategies to maintain abstinence among spontaneous quitters, and we conclude the article with gaps identified in the literature that warrant further study.