Adolescent girls in Denmark use oral contraceptives at an increasingly young age, and with more pauses and shifts.

INTRODUCTION Use of hormonal contraceptives for birth control is commonplace in the Western World. In Europe, there is considerable variety in the frequency of use of hormonal contraceptives and in the age at which these contraceptives are initiated. The purpose of the present study was to describe the use of hormonal contraceptives among the Danish adolescent female population, focusing on age, period and cohort effects and including types of hormonal contraceptives. MATERIAL AND METHODS All women aged 14-50 years during the 1995-2012 period were identified through the Central Person Register. Furthermore, the National Registry of Medicinal Products Statistics provided information on redeemed prescriptions for hormonal contraceptives characterised by Anatomical-Therapeutic-Chemical (ATC) classification codes. RESULTS At the age of 17 years, more than 50% of the Danish adolescent population had redeemed a prescription for hormonal contraceptives. At the age of 20 years, 85% had ever used hormonal contraceptives. This amounts to a significant decrease in age at which hormonal contraceptives were initiated in the younger birth cohorts compared to the older cohorts. Additionally, adolescent girls have more pauses and shifts between types of hormonal contraceptives. Since 2010 there has been a shift toward use of second generation oral contraceptives away from third and fourth generation contraceptives. CONCLUSION Adolescent girls tend to initiate their use of oral contraceptives at a younger age than the older cohorts do. Furthermore, they have more pauses and shift between products more frequently than older cohorts. The type of oral contraceptive used has shifted since 2010 towards older products with second generation progestins. FUNDING The study was funded by salaries from North Zealand Hospital. TRIAL REGISTRATION The study was approved by the Danish Data Protection Agency (J. No. 2010-41-4778).