About 16 million adolescent girls between 15 and 19 years of age give birth each year. Babies born to adolescent mothers account for roughly 11% of all births worldwide, with 95% occurring in developing countries. For some of these young women, pregnancy and childbirth are planned and wanted, but for many others they are not. There are several factors that contribute to unplanned and unwanted pregnancies in adolescence. These publication’s two main objectives are to: identify effective interventions to prevent early pregnancy by influencing factors such as early marriage, coerced sex, unsafe abortion, access to contraceptives and access to maternal health services by adolescents; and provide an analytical framework for policy-makers and programme managers to use when selecting evidence-based interventions that are most appropriate for the needs of their countries and contexts.