Method Characteristics of the LNG-IUS

This section of the IUD Toolkit presents the latest information on Method Characteristics for the LNG-IUS IUD as of January 2009.

See also: Client Attitudes and Behaviors Regarding the LNG-IUS | Service Delivery and the LNG-IUS | How Organizations and Providers Can Obtain the LNG-IUS | Bibliography

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Hormone Releasing System

  • The T-shaped LNG-IUS releases 20 µg daily of levonorgestrel (the progestin widely used in implants and oral contraceptive pills) directly into the uterine cavity. This ensures high hormonal concentration in the endometrium and adjacent tissues and low hormonal levels in the blood stream. Thus, systemic side effects are minimized. Plasma levels of levonorgestrel with the LNG-IUS are lower than those seen with subcutaneous implants, combined oral contraceptives, and progestin-only pills (Jensen, 2005; Sturridge and Guillebaud, 1996).


  • The LNG-IUS, like the copper-bearing TCu-380A, is a highly effective form of long-acting, reversible contraception. A review of studies conducted over the past 20 years showed that the LNG-IUS has a five-year cumulative pregnancy rate of < 0.5 percent. This means that over 5 years of use of the LNG-IUS, only 5 women out of 1,000 will become pregnant (Thonneau and Almont, 2008).

Return to Fertility

Lifespan after Insertion of LNG-IUS

  • The LNG-IUS is effective for up to five years after insertion (Jensen, 2005); some evidence suggests that it may be effective for up to seven years (Sivin et al., 1991). In the United States, the Food and Drug Administration has labeled the LNG-IUS, commercially marketed as Mirena®, as effective for five years (USFDA, 2008).

Mechanism of Action

  • Levonorgestrel released by the LNG-IUS into the uterine cavity has several local effects, including thickening of the cervical mucus and inhibiting sperm movement. It also suppresses the growth of the endometrium. In addition, the LNG-IUS, like copper-bearing IUDs, creates a foreign-body reaction in the uterine cavity that hinders sperm and ovum transport, which prevents fertilization. In all cases, the LNG-IUS prevents pregnancy prior to implantation (Jensen, 2005).

Side Effects

Menstrual changes

  • Use of the LNG-IUS may be associated with bleeding irregularities that tend to stabilize within 3 to 6 months after insertion (Andersson et al., 1994; Mansour, 2007; Ibraheim et al., 2005). Long-term use of the LNG-IUS often leads to decreased menstrual bleeding, oligomenorrhea (infrequent bleeding), or amenorrhea (absence of bleeding) (Diaz et al., 2000; Grimes et al., 2007). Approximately 17 percent of women will experience amenorrhea at 1 year after insertion, and as many as 60 percent will be amenorrheic with long-term use (Mansour, 2007).  All bleeding irregularities are reversible and do not negatively impact users’ health (Zhang, 2001).

Systemic hormonal side effects

  • Because systemic absorption of the levonorgestrel released by the LNG-IUS is low, hormonal side effects are less pronounced than with many other hormonal methods. These side effects are often transient and include acne, headache, mood disturbance, dizziness, breast sensitivity, nausea, and fluid retention (Mansour, 2007; WHO, 2007). Only 1 percent to 2 percent of women discontinue use of the LNG-IUS because of systemic side effects (Mansour, 2007). A small number of LNG-IUS users will develop simple ovarian cysts because plasma levonorgestrel levels disrupt ovulation in some cycles and cause enlarged follicles (Bayer, Inc., 2008). These cysts can cause pelvic pain, but in most women they are asymptomatic and do not require any treatment; 94 percent of cases resolve spontaneously within 6 months (Inki, 2002; Mansour, 2007).

Non-Contraceptive Health Benefits

  • It is well documented that the LNG-IUS is an effective treatment option for women suffering from idiopathic menorrhagia (heavy, prolonged menstrual bleeding) (Andersson et al., 1990; Xiao et al., 2003; Kriplani et al., 2007). Idiopathic menorrhagia occurs in 20 percent to 30 percent of women of reproductive age and can cause or worsen anemia, particularly among women in developing countries where iron deficiencies are common. The LNG-IUS is an attractive treatment alternative to hysterectomy (surgical removal of the uterus), especially for women who cannot access surgical care or who are interested in preserving their fertility (Barrington and Bowen-Simpkins, 1997; Hurskainen, 2004; Kriplani et al., 2007). It is also comparable to other minimally invasive methods of treatment of excessive bleeding (Jensen, 2002), and it is medically superior to a regimen of oral progestins (Grimes et al., 2007). Cost-effectiveness analysis reveals that indirect and direct costs of using the LNG-IUS to treat menorrhagia are substantially less than those for hysterectomy (Hurskainen, 2004).  A study in India demonstrated that in addition to being an effective method of treatment, the LNG-IUS was well accepted by patients for the management of menorrhagia (Kriplani et al., 2007).
  • In addition, the LNG-IUS has been used for the treatment of endometriosis (a condition that occurs when functioning endometrial tissue grows in places other than the uterus which may result in severe abdominal discomfort and painful, excessive menstrual bleeding), adenomyosis (a condition that occurs when endometrial tissue is found within the muscular layer of the uterus), and dysmenorrhea (painful menses), and for endometrial protection during estrogen replacement therapy (Jensen, 2002; Jensen, 2005; Mansour et al, 2007). Preliminary evidence also suggests that the LNG-IUS may be used to treat menorrhagia associated with uterine fibroids and endometrial hyperplasia (excessive growth of the endometrium) (Varma et al., 2006). reveal an overall rate of ectopic pregnancy of 0.06 per 100 women who used the method for a year (which is about 6 ectopic pregnancies in 10,000 women over a one-year period) (Backman et al., 2004). These rates are lower than the estimated rate of ectopic pregnancy of 0.3 to 0.5 per 100 woman-years for women using no contraceptive method (which amounts to 30 to 50 ectopic pregnancies per 10,000 women over a one-year period) (Penney et al., 2004; Sivin, 1991). Use of the LNG-IUS is not contraindicated for women who have had an ectopic pregnancy in the past (WHO, 2004a). Despite the low risk in LNG-IUS users, ectopic pregnancy is a serious and life-threatening event, so providers must be aware of its signs and symptoms.


  • Perforation of the uterus during insertion is very rare. In a large observational cohort study, the rate of perforation was 0.9 per 1,000 insertions. The skill and experience of the provider is the most important factor that minimizes the risk of perforation (Harrison-Woolrych et al., 2003).


  • Expulsion of the LNG-IUS is uncommon. Over 5 years of use, spontaneous expulsion will occur in approximately 5 percent of users (Mansour, 2007). In a recent review, the LNG-IUS was associated with a slightly higher rate of spontaneous expulsions than were copper IUDs with >250 mm2 copper surface area, such as the TCu-380A (Grimes et al., 2007). Expulsion rates with the LNG-IUS do not vary by parity (Prager and Darney, 2007).

Ectopic Pregnancy

  • Because it is so effective in preventing pregnancy, the LNG-IUS protects well against ectopic pregnancy. In the unlikely event that a woman with the LNG-IUS becomes pregnant, the chance of that pregnancy being ectopic is increased. However, because pregnancies are so rare among LNG-IUS users, the absolute number of ectopic pregnancies is still much smaller than among women who use no contraception. Data from prospective, randomized clinical trials reveal that the 5-year cumulative rate of ectopic pregnancy ranges from 0.06 to 0.5 per 100 women with use of the LNG-IUS. In a cross-sectional survey study, the rates of ectopic pregnancies were 0.045 and 0.22 per 100 women at 1 and 5 years, respectively (Backman et al., 2004). These rates are lower than the estimated rate of ectopic pregnancy of approximately 2 per 100 women of reproductive age in the general population (Murray et al., 2005). Use of the LNG-IUS is not contraindicated for women who have had an ectopic pregnancy in the past (WHO, 2004a). Despite the low risk in LNG-IUS users, ectopic pregnancy is a serious and life-threatening event, so providers must be aware of its signs and symptoms.

STI-Related Health Risks

Pelvic Inflammatory Disease (PID)

  • Rates of PID are very low among LNG-IUS users. In one study, the cumulative 36-month rate of PID was 0.5 among LNG-IUS users (compared with 2.0 in copper Nova-T users) (Toivonen et al., 1991).
  • Researchers have found that an increased risk of PID exists within the first 20 days after insertion of copper IUDs (Prager and Darney, 2007; FFPRHC, 2004). PID in IUD users is usually caused by (recognized or unrecognized) sexually transmitted infections (STIs)  when the organisms chlamydia trachomatis or gonococcus are spread during the insertion from the cervical canal to the upper reproductive tract. PID is not caused by the IUD itself (Grimes, 2000). After the first 20 days, PID is a very uncommon event (ACOG Committee, 2005). Although there are no comparable data for the LNG-IUS regarding the risk of PID following insertion, it is reasonable to expect that a similar increase in risk exists within the first 3 to 4 weeks of use if cervical infection is present. This is why the LNG-IUS should not be inserted if a woman has a current case of gonorrhea or chlamydia or if she might have been exposed to these STIs due to individual risk factors. After the first 3 to 4 weeks following insertion, PID risk in LNG-IUS users should be minimal. In fact, some preliminary physiologic and clinical evidence indicates that the LNG-IUS may actually help protect against PID (Prager and Darney, 2007; Toivonen et al., 1991; WHO, 2007).


  • The use of the LNG-IUS does not increase the risk of infertility among parous or nulliparous women (Prager and Darney, 2007). In a study examining the relationships between infertility, IUD use, and sexually transmitted bacteria, the risk of infertility due to tubal damage was not associated with previous IUD use, but rather to past exposure to chlamydia trachomatis (Hubacher et al., 2001). Although this study addressed the relationship between use of copper IUDs and infertility, the findings can be extrapolated to use of the LNG-IUS. Moreover, the LNG-IUS may have a protective effect against PID, and thus, against tubal infertility (Prager and Darney, 2007).
  • A review of IUD studies found that pregnancy rates after IUD removal were similar to rates among the general population. While some data on LNG-IUS users were included in this review, the author acknowledges that further research is needed to address the question of whether LNG-IUS use impacts subsequent fertility (Skjeldestad, 2008).


  • A recent study demonstrated that LNG-IUS use by women with HIV does not increase genital shedding of the virus. Among LNG-IUS users with HIV, bleeding patterns, ovarian function, and body iron stores are similar to those among users without HIV (Heikinheimo et al., 2006). For women with HIV who experience menorrhagia, the LNG-IUS may be used as an alternative to uterine surgery (Lehtovirta et al., 2007).