Teenage pregnancies are often not intended, and there is a high risk that unintended pregnancies will lead to abortion. The wide-spread availability of Youth Clinics, the subsidizing of contraceptives and the introduction of new and effective contraceptives have failed to lower the abortion rates. The aim of this thesis was to study possible risk groups and to highlight underlying reasons for contraceptive failure. Methods: Study I and II were quantitative studies with the aims of investigating whether teenagers who sought emergency contraception (Paper I) and teenage mothers (Paper II) were at risk for new unintended pregnancies during a 12-month follow-up period. Study III and IV were qualitative studies. The aim in study III was to see how contraceptive use was documented in medical records (MRs) concerning teenagers who had attended for induced abortion. In study IV the aim was to find out reasons for non- use or inconsistent use of contraceptives among teenagers attending for abortion. Results: In study I and II data were collected from medical and antenatal records. The results showed that both groups, despite contraceptive counselling, were at high risk for new unintended pregnancies leading to abortion. Attendance at the postpartum visit was low and 24% of the teenage mothers did not receive any recommendation about using a particular contraceptive method. Within 12 months 25% had a new pregnancy and of these one third led to legal abortion. In Study III two themes were generated from the analysis of the MRs; ‘Contraceptive methods previously used’ and ‘Plan for future contraceptive use’. All MRs did not contain information about contraceptive use. In study IV one theme was generated from the analysis of the interview text: ‘Struggling with feelings of uncertainty and patterns of behaviour’. Conclusion: Teenagers using emergency contraceptive pills and teenage mothers were at high risk for unintended pregnancies. Contraceptive failure in teenagers who have had an abortion may be due to in part to the absence of contraceptive counselling at abortion visits and in part to problems with contraceptive use due to insufficient knowledge and not knowing what do when side-effects occurs.