Purpose: To assess longitudinally the relationship between knowledge about sexually transmitted diseases (STDs) and sexual behaviour, contraceptive use, STD protection and social class in a group of Swedish teenage girls.
Methods: Girls starting their upper secondary school education were invited to attend a teenage clinic during a period of 2 years (5 visits). Questions were asked about family situation, sexual activity, contraceptives, STD protection and knowledge about STD. Gynaecological examinations were performed on entry and completion, and when necessary during the observation period.
Results: Eighty-eight girls completed all visits during the observation period. At 16 years of age there were no significant differences in knowledge about various STD and STD protection between girls from different social classes or with respect to coital experience, age of coitarche and the subsequent number of sexual partners at 18 years of age. At 18 years of age there was a better knowledge about STDs and the need for STD protection (p < 0.01) among girls with coital experience compared with those who had no coital experience. Girls reporting many lifetime partners were best informed, but in spite of solid knowledge they did not protect themselves from infection. Even though 34% of the girls with coital experience were found to harbour a STD during the course of this study, almost all girls denied the possibility of having acquired or transmitted an infection.
Conclusions: Although girls were well-informed about sexually transmitted diseases and knew how to avoid infections this knowledge had little influence on behaviour.