Background: Adolescent reproductive health is part of internationally agreed development goals. Unmarried adolescents are not commonly included in global monitoring of contraceptive usedespite the more severe consequences of unintended childbearing for them. Objective: We document levels and trends of contraceptive prevalence and demand for married and sexually active unmarried adolescent women aged 15-19 in Latin America and sub-Saharan Africa. We estimate the effect of adolescent contraceptive use and marital status on fertility and the impact of meeting current demand. Methods: We propose a fertility model informed by the proximate determinants framework separating adolescents by marital status. Linear Mixed Model estimates are based on aggregate data from 120 DHS surveys for 34 developing countries. Results: Increasing contraceptive prevalence has already reduced adolescent fertility by 6.8Š in Latin America and 4.1Š in sub-Saharan Africa. Meeting the total demand for contraceptives of unmarried adolescents would lead to an additional decrease in fertility of 8.9Š and 17.4Š respectively. Conclusions: Contraceptive demand and prevalence are generally higher for sexually active unmarried adolescent women than for those married. Increasing prevalence has already had an impact in declining fertility, but there is a potentially larger effect if high levels of unmet need are eliminated, particularly in sub-Saharan Africa. Such reduction would have a significant impact on adolescent health. Contribution: We provide evidence of the importance of contraceptive use of unmarried sexually active adolescent women in explaining trends in adolescent fertility. We estimate the potential effect of meeting the contraceptive needs of married and unmarried adolescents on unintended childbearing.