Benefit-Risk Assessment of the Levonorgestrel Intrauterine System in Contraception

The levonorgestrel-releasing intrauterine system (IUS) is a long-acting, fully reversible method of contraception. It is one of the most effective forms of contraception available, and combines the advantages of both hormonal and intrauterine contraception. The levonorgestrel-releasing IUS also gives the users many non-contraceptive benefits: the amount of menstrual bleeding and the number of days of menstrual bleeding are reduced, which makes it suitable for the treatment of menorrhagia (heavy menstrual blood loss). Dysmenorrhoea (painful menstruation) and premenstrual symptoms are also relieved. In addition, the levonorgestrel-releasing IUS provides protection for the endometrium during hormone replacement therapy.

The local release of levonorgestrel into the uterine cavity results in a strong uniform suppression of the endometrial epithelium as the epithelium becomes insensitive to estradiol released from the ovaries. This accounts for the reduction in menstrual blood loss. All possible patterns of bleeding are seen among users of the levonorgestrel-releasing IUS; however, most of the women who experience total amenorrhoea continue to ovulate. The first months of use are often characterised by irregular, scanty bleeding, which in most cases resolves spontaneously. The menstrual pattern and fertility return to normal soon after the levonorgestrel-releasing IUS is removed.

The contraceptive efficacy is high with 5-year failure rates of 0.5–1.1 per 100 users. The absolute number of ectopic pregnancies is low, as is the rate per 1000 users. The levonorgestrel-releasing IUS is equally effective in all age groups and the bodyweight of the user is not associated with failure of the method.

In Western cultures continuance rates among users of the levonorgestrel-releasing IUS are comparable with those of other long-term methods of contraception. Premature removal of the device is most often associated with heavy menstrual bleeding and pain, as with other long-term methods of contraception, and is most common in the youngest age group. When adequately counselled about the benign nature of oligo- or amenorrhoea, most women are very willing to accept life without menstruation. The risk of premature removal can be markedly diminished with good pre-insertion counselling, which also markedly increases user satisfaction. User satisfaction is strongly associated with the information given at the time of the levonorgestrel-releasing IUS insertion. Thus, the benefits of the levonorgestrel-releasing IUS make it a very suitable method of contraception for most women.