Teen pregnancy is a social problem not resolved in developing and some developed countries. Adolescent fecundity has become the most exact bio-demographic and health indicator of development. In developing countries that are expected to follow the sexual behaviour patterns of developed countries, without offering the levels of education and services for adolescents, the consequences will be adolescent fecundity and STI prevalence increase. The ignorance about sexuality and reproduction both in parents, teachers and adolescents increases the early initiation of coital relations and of unwanted pregnancies. Extreme poverty and being the son or daughter of an adolescent mother are risk factors of repeating the early pregnancy model. The application of predictive risk criteria in pregnant adolescents to facilitate the rational use of Health Services to diminish the maternal and perinatal mortality is discussed as well as the social factors associated with adolescent pregnancy as socioeconomic levels, structure - types and characteristics of the family, early leaving school, schooling after delivery, female employment, lack of sexual education, parental and family attitudes in different periods of adolescent pregnancy, adolescent decisions on pregnancy and children, unstable partner relationship and adoption as an option. Social consequences are analyzed as: incomplete education, more numerous families, difficulties in maternal role, abandonment by the partner, fewer possibilities of having a stable, qualified and well-paid job, greater difficulty in improving their socioeconomic level and less probability of social advancement, lack of protection of the recognition of the child. Finally, based on evidence, some measures that can reduce adverse consequences on adolescent mothers, fathers and their children are suggested.