Review articleThe levonorgestrel intrauterine system in nulliparous women
Introduction
The levonorgestrel intrauterine system (LNG-IUS), known as Mirena (or LevoNova in Scandinavia), was first introduced in Finland in 1990. Since then, it has been approved for use in over 100 countries and has had approximately 7 million users [1]. In multiple trials, it has been shown to be a safe, effective and acceptable method of contraception, with few side effects or negative sequelae [2], [3], [4]. Its contraceptive efficacy is comparable to, if not higher than, surgical sterilization, and its use leads to many noncontraceptive benefits, including improvement in anemia, menorrhagia and endometriosis, control of uterine fibroids and adenomyosis, and possible protection against and treatment of endometrial hyperplasia and cancer [5], [6]. However, most trials of the LNG-IUS and other forms of intrauterine contraception (IUC) limited enrollment to parous women. The limited data in nulliparous women, as well as misunderstandings about the relationship between IUC and pelvic inflammatory disease (PID), have caused concerns about its use in nulliparous women. Worries about IUC for nulliparous women come largely from misinformation about the risk of infertility associated with IUCs, but clinicians also worry that they might be less effective and cause more side effects, making them less acceptable to nulliparous women. We will address the use of the LNG-IUS in nulliparous women with respect to several important outcomes which, we believe, mitigate these concerns.
Section snippets
Mechanical issues
Any intrauterine device must fit within the contours of the uterine cavity. In general, parous, reproductive-aged women have higher uterine volume and a greater endometrial surface area than nulliparous and nulligravid women [7]. Clinicians are concerned that a smaller cavity may increase the risk of failure due to expulsion, perforation or early discontinuation of IUC in nulliparas compared to parous women.
While studies have attempted to estimate the risk of perforation from IUC insertion, few
Efficacy and acceptability
The overall efficacy of the LNG-IUS is excellent, with rates ranging from 0 to 1.1 pregnancies per 100 woman-years of use [2], [8], [14]. A recent prospective, noncomparative study evaluated efficacy by parity and found no pregnancies at 1 year in either 143 parous or 92 nulliparous women. In this study [14], two different LNG-IUSs were used, the Femilis and the Femilis Slim, which were designed for use in nulliparous women. Neither is yet approved for general use. However, it is still
Pelvic inflammatory disease and infertility risks
Patients and providers often express concern about the possible relationship between IUC use and both PID and subsequent infertility. This presumed relation is especially concerning for nulliparous women who do not yet know if they can become pregnant. Numerous studies in the 1970s and 1980s found an increased risk of PID and infertility in IUC users [17], [18]. Many of these studies were reanalyzed, demonstrating that most of the increased risk was associated with one type of IUC no longer
Use after abortion
Between 39% and 52% of all abortions are obtained by nulliparous women [25], [26]. Most women who present for abortion have experienced a contraceptive failure and are at high risk for another pregnancy, thus making them good candidates for a highly efficacious contraceptive method like IUC. Placement of IUC immediately following an abortion is ideal, given an already dilated cervix, minimal additional discomfort for the patient, certainty that the patient is not pregnant and peace of mind for
Conclusion
Although we need more information about the benefits and risks of LNG-IUS use in nulliparous women, there are extensive data about the equivalent efficacy and safety of the LNG-IUS and other currently available IUC methods in nulliparous and parous women. In order to provide young women, many of whom are nulliparous, with the most effective methods of contraception, we believe that the LNG-IUS can be offered to nulliparous women, for whom the device appears to be both safe and extremely
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