ALT Resumen Sexual and reproductive health, including union and adolescent pregnancy, is a multidimensional and multisectoral phenomenon in which various factors converge and are expressed unequally among socioeconomic groups. The aim of this paper is to analyze the relationship between the decline in adolescent fertility and social and territorial inequality in five Latin American cities. For this purpose, we used the exploitation of population censuses from the 1990, 2000, 2010 and 2020 census rounds through indicators of polarity, correlation, and specific rates. The main results suggest that inequality in union and childbearing among adolescents increased markedly in general terms in all cities, both because of the lagged fall among poorer adolescents and the decline among richer adolescents. La salud sexual y reproductiva, que incluye la unión y el embarazo adolescente, es un fenómeno multidimensional y multisectorial en el cual concluyen diversos factores, que operan o se expresan