Trends in initiation of hormonal contraceptive methods among teenagers born between 1989 and 1997 in Norway and the United States.

Objective: To assess initiation of hormonal contraception among women aged 15-19 in the US and Norway by birth cohort.

Study Design: We used population-based survey (US) and administrative (Norway) data to estimate the cumulative probability of age at first use of hormonal contraception for female residents born between 1989 and 1997 in 3-year birth cohorts. Differences between countries were assessed using confidence intervals, and differences between birth cohorts were assessed using survival analysis.

Results: At age 15, first use of any hormonal method was higher among US respondents (16%-17% US vs 10%-13% Norway), whereas for ages 16 to 19 use was higher among Norwegian women (by age 19, 60%-64% US vs 76%-78% Norway). Similar patterns were observed for pill use; however, depot medroxy-progesterone acetate (DMPA), implant, and intrauterine device (IUD) use tended to be higher among US women. In both countries, cumulative first use of the pill, patch, ring, and DMPA declined across birth cohorts while first use of implants and IUDs increased.

Conclusion: Age at initiation and type of first hormonal method use differed between US and Norwegian teenagers. These differences may contribute to the lower teen birth rate in Norway.

Implications: Age at initiation of hormonal contraception among teenagers is earlier in Norway than in the United States, and types of hormonal methods used vary. These differences may contribute to the lower teen birth rate in Norway.