BACKGROUND There are legal regulations about sexual and reproductive rights of adolescents. However, this legal framework (LF) may have contradictory elements: there are laws assuring confidentiality and access to contraception at any age but there are other laws that consider any sexual contact with an adolescent younger than 14 a sexual assault, whose report to the legal authorities in mandatory. OBJECTIVE To explore the knowledge and clinical practice of primary health care (PHC) providers regarding prevention of teenage pregnancy. METHODS Qualitative study collecting data using semi-structured interviews made to midwives and directors of PHC centers. Analysis of the data was based on Grounded Theory. RESULTS There is a differentiated clinical care for pregnancy prevention among adolescents if they are over 14 years old. This is due to the LF, specifically to the sexual crime’s law (19,927) and the law about regulation of the fertility (20,418). The differences affect health care, access and counseling about contraception and confidentiality. Healthcare of teenagers under the age of 14 is perceived as problematic for providers, due to the possible legal implications. CONCLUSIONS The LF causes insecurity on health care providers and derives in a differentiated clinical approach according to the patient´s age. This is a barrier to provide timely and confidential access to counseling and contraception.