No change in adolescents' neglect on contraceptive use over two decades.

Purpose: The sexual activity and contraceptive use is evaluated over 21 years amongst Danish adolescents in ninth grade.

Methods: A repeated, cross-sectional questionnaire study in the municipality of Viborg, comparing the results of four consecutive surveys between 1986 and 2007.

Results: In 2007, 40% of the pupils had sexual debut at an average age of 15.3 ± 1.5 years. At sexual debut condoms were used in 77% of the adolescents and the contraceptive pill in 15%. At their latest coitus 34% used any contraceptive pill as 27% of pupils changed from use of condom to the pill. Practical experience with condoms was found in 90% of both sexes at sexual debut. Fourteen percent of the adolescents used no contraception at all at debut in 2007, which is similar to 1986, 1993, and 2000. Eighteen percent of the pupils used no contraception at all at their last intercourse in 2007 and 2000.

Conclusion: Knowledge about and use of condoms is substantial amongst adolescents already at sexual debut. A shift is confirmed from condoms at first coitus to more frequent use of the pill later on. A considerable number of pupils (10-20%) are neither protected against sexually transmitted infections nor pregnancy at first or later intercourse.