In developing countries, young women between 15 and 24 years of age account for more than 40% of unsafe abortions due to the high number of unwanted and/or out-of-wedlock pregnancies. However, much about the profile of adolescents and young women who usually experience premarital pregnancies remains unknown. This study sought to understand the risk of pregnancy before marriage among adolescents and young women in Ouagadougou, Burkina Faso. By using longitudinal data from a demographic surveillance system, we tested the explanatory power of two theoretical assumptions on premarital childbearing in sub-Saharan Africa, which assumptions are the cultural inheritance model and the social capital model. The results confirmed the explanatory power of the cultural inheritance model on the one hand and partially confirmed the power of the social capital model on the other hand. These results highlight the need for a multipronged approach to sexual and reproductive health for young people. Efforts against premarital pregnancies among adolescents and young women would be more effective if they were based on participatory approaches, incorporating actions at both community and institutional levels, as suggested by the recent Global Accelerated Action for the Health of Adolescents logical framework.