Original research articleA nationwide cohort study of the use of the levonorgestrel intrauterine device in New Zealand adolescents
Introduction
The Mirena® levonorgestrel intrauterine device (LNG-IUD) is licensed in New Zealand for contraception, treatment of menorrhagia and endometrial protection during estrogen replacement therapy (http://www.medsafe.govt.nz/profs/datasheet/m/Mirenaius.htm). The use of the LNG-IUD is well established in the adult population, but there have been no research studies specifically on the use of the LNG-IUD in adolescents. The majority of studies that have included adolescents had only a small number of 18- to 20-year-olds with no relevant subgroup analysis.
Adolescence is a variable time period from the onset of puberty until the transition to adulthood. The World Health Organization (WHO) Medical Eligibility Criteria for Contraceptive Use assigns the LNG-IUD to “Category 2” for women less than 20 years old, which indicates that the method may generally be used but that more careful follow-up is required [1]. Recent reviews and editorials have challenged long-held views that IUDs should not be used in young women [2], [3], [4], [5], [6]. The 2007 American College of Obstetrics and Gynaecology Committee Opinion Intrauterine Device and Adolescents concluded that data support the safety of IUDs for most women, including adolescents [7].
The primary aims of this nationwide cohort study were to determine the indications for insertion of the LNG-IUD in New Zealand adolescents (including comorbidities influential in the decision to use the device) and to establish patterns of use, including duration of use of the LNG-IUD in the adolescent population and reasons for removal.
Section snippets
Methods
The Intensive Medicine Monitoring Program (IMMP) performs post-marketing surveillance of selected medicines, usually those newly introduced to the New Zealand market. Prospective observational cohort studies are conducted using prescription-event monitoring (PEM) methods in which cohorts of patients are established from prescription data and are then followed up, primarily by questionnaires to prescribers [8]. Spontaneous reports of adverse events for intensively monitored medicines are also
Results
A total of 179 adolescents with LNG-IUD insertions prior to January 1, 2007, were identified from the IMMP data sets. Of these 179 cases, 2 did not meet the inclusion criteria (Fig. 1), and therefore questionnaires were sent out for 177 adolescents.
Because each case had a different insertion date, the duration of follow-up varied for each adolescent as is usual in PEM studies. The period to follow-up (time of insertion to date of questionnaire return) ranged from 7 months to 8.9 years. For the
Discussion
While it is estimated that the Mirena® IUD has been used by 7 million women worldwide (Bayer Schering Pharma web site: http://www.asia.mirena.com/scripts/en/1_what_is_the_ius/is_it_safe/index.php; accessed 5/7/2008), this is the first study to specifically address its use in an adolescent population. Despite the limited research upon which to base clinical practice of LNG-IUD use in adolescents, approximately half of New Zealand gynecologists have used the device in an adolescent [14]. The IMMP
Conclusion
This nationwide study is the first specific assessment of LNG-IUD use in an adolescent population. The principal findings were as follows: the wide range of indications for insertion of the LNG-IUD in the adolescent population including endometriosis, dysmenorrhea and menstrual management; a low expulsion rate; and a high continuation rate of 85% at 1 year. Further research into the safety and efficacy of the LNG-IUD in adolescents especially in the management of off-label indications is
Acknowledgments
This study was carried out in partial fulfillment of the requirements for a Masters of Medical Science degree with the University of Otago and with the support of the IMMP. There was no external funding source.
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