Pregnancy during adolescence represents a challenge to society as a whole. Its incidence is increasing and brings about social and medical consequences to both the teen mothers and their children. The purpose of this study was to evaluate pregnant teenager involvement in sexual activity and the social context. The group studied comprised 152 pregnant teenagers attending the Department of Pediatrics, Santa Casa de Sao Paulo (SCSP) General Hospital. All information was analyzed. The age at first intercourse was 14.2 years and the average period between first intercourse and pregnancy was 1.4 years. Most pregnancies (75%) were neither planned nor wanted, however, most teen mothers (64.3%) did not use any contraceptive method. Of the pregnant teenagers, 68.1% came from unstructured families where in 71% of the teen pregnancy cases, there was a role model (mother, sister, or cousin who already experienced teen pregnancy). The average number of school years attended by the analyzed pregnant teenagers was 8.1 years, however, there was a high dropout rate of 40.1%. The age at first intercourse was low and concurs with the high incidence of unstructured families. The average number of school years attended was high, which would theoretically reflect a greater knowledge with regard to human reproduction, pointing to the multicausality of teen pregnancy and the role played by the family. Conclusions: We confirmed that teen pregnancy presents multicausal etiology; sexual initiation of pregnant teenagers was quite early with high dropout rates, which indicated that prevention methodology should be based on early detection of risk factors for elaboration of appropriate prevention proposals.