Objective:The objective of this study was to identify the main factors associated with pregnancy in a sample of adolescents enrolled in school, between 13 and 19 years of age in Buenaventura, Colombia.Methods: A prospective analytical study of a cohort of 316 adolescents between 13 and 19 years old was conducted in public and private schools in Buenaventura between 2006 and 2007.In the first measurement, adolescents should not be pregnant.A questionnaire was applied based on a theoretical model involving several levels and constructs.Six months later a pregnancy test was done.The study was endorsed by the Institutional Ethics Committee.Multiple logistic regression analysis was performed to look for risk factors and protectors for the pregnancy event.Results: The average age of the cohort was 15.9 years, 10% of teenage girls became pregnant during the follow-up.The average age of first sexual intercourse was 14.5 years, 67.7% indicated that no family planning method used at first intercourse.During follow-up, adolescents who were at greatest risk for pregnancy were those who reported in the survey: Not being able to avoid sexual intercourse when they did not use planning methods; feeling guilty about alcohol; having friends who aborted and feeling pressure to start sex life.Conclusions: The risk factors and protectors of an early pregnancy are not only at the individual level, but also encompass the peer and adolescent family as well as the health services.In terms of public health, it implies that efforts to reduce early pregnancies in Buenaventura should be directed towards these three levels.