Intrauterine System (IUS)

The IUS is a levonorgestrel (LNG) releasing intra-uterine contraceptive device (IUCD). The Mirena coil is the only LNG-IUS currently available in the UK. It has a plastic T-frame with a reservoir containing 52 mg of levonorgestrel and releasing 20 mcg/24hours. ¹ Lower dose (10 and 14 mcg/24 hours) and smaller size LNG-IUS are currently under clinical development.²
It has been licensed as a contraceptive in the UK since 1995 and more recently for the treatment of idiopathic menorrhagia.

Only 1% of contraception-using women use it as their method of choice³ and this has remained stable over the last few years despite its benefits and NICE guidance⁴ that all women requesting contraception should be offered a choice including long-acting reversible methods (such as the IUS).

• Suppression of the endometrium which prevents implantation.⁵
• Decreased sperm penetration of cervical mucus and impaired sperm migration within the uterus.
• Minimal effect on the hypothalamic-pituitary-ovarian axis - suppression of ovulation in <25% women.

Contraceptive use

• Highly efficacious with a failure rate of less than 1 per 100 women years. The IUS has a Pearl index of 0.18 per 100 women years (the Pearl index of a contraceptive method represents the number of pregnancies experienced during 100 women years of its use). ^4,5,6 This is similar to modern non-hormonal IUCDs⁷ and male sterilisation.⁴
• The LNG-IUS is a suitable option for most women who need contraception with few conditions where risks of use outweigh benefits (see contraindications). Its niche to-date has been as contraception for multips with heavy periods. It can be appropriate for many other women including those who traditionally offer contraceptive challenge such as obese women, women with diabetes or epilepsy, women with migraine and women with contraindications to oestrogen (see contraception and special groups).^4,5,6
• The LNG-IUS should not be used as emergency contraception.

Advantages as a contraceptive method include

• Highly effective method with rapid return of fertility post-removal.
• Reduced menstrual loss and dysmenorrhoea.
• Convenience - independent of intercourse and long-lasting.
• Some studies have suggested a possible reduction in pelvic inflammatory disease compared to copper IUCDs, but this has not been supported by systematic review. ⁸
• No significant interaction with hepatic enzyme-inducing drugs since progesterone action is largely local.
• No effect on bone mineral density (comparable to non-users after 7 years' use).⁹

Disadvantages include

• Menstrual irregularity frequently occurs in the first half year of use.
• Progesterone-related side effects in a minority of women (eg mastalgia, depression and mood swings, acne).
• Functional ovarian cysts may develop but usually resolve spontaneously.
• Method of fitting may be unacceptable to some women and the IUS has a larger diameter than some IUCDs and fitting may be more difficult in some women, particularly nullips or perimenopausal women and may require local anaesthetic.
• No protection against sexually transmitted infections (STIs).
• Risk of expulsion or displacement - the most likely cause of LNG-IUS failure is the risk of expulsion, occurring in 1 in 20 women.⁴

Non-contraceptive uses

Menorrhagia

• The LNG-IUS is the first-line pharmaceutical treatment for menorrhagia (where hormonal methods are acceptable and ongoing treatment of at least a year is anticipated) and can reduce menstrual losses by over 90%. ^10,11
• It is effective even in the presence of fibroids, although it is not generally recommended where fibroids distort the uterine cavity because of difficulties with insertion.
• The LNG-IUS is more effective than medical treatments for the treatment of menorrhagia (but trial quality is poor).
• Surgical treatment (hysterectomy, endometrial resection or ablation) is more effective at reducing menstrual blood loss at 1 year but the LNG-IUS is as effective at improving quality of life at 1 year. ¹²
• Interestingly, a recent trial has suggested that sexual function is better post-hysterectomy for women with menorrhagia than for those treated with a LNG-IUS.¹³
• Cost of treatment for menorrhagia is significantly lower in women with LNG-IUS compared to hysterectomy.¹⁴

Hormone Replacement Therapy

• The LNG-IUS is licensed (since 2004) for the prevention of endometrial hyperplasia during oestrogen replacement therapy. ⁵
• Potentially a means of delivering endometrial protection with minimum systemic absorption of progestogen, given concerns regarding increased breast cancer risk associated with combined HRT.
• A RCT showed that a 10 mcg/24 hour IUS device (not currently available) was as effective as the Mirena in providing endometrial protection in post-menopausal women on oestrogen therapy but had the advantage of easier insertion and less effect on serum lipid profiles¹⁵.

Other potential uses of the IUS which are currently being explored include the treatment of:

• Endometriosis and adenomyosis
• Fibroids
• Endometrial hyperplasia
• Early stage endometrial carcinoma in a patient unfit for surgery²

• Pregnancy¹⁶
• Recent sexually transmitted infection (unless fully investigated and treated)
• Undiagnosed uterine or vaginal bleeding
• Distorted or small uterine cavity
• Genital malignancy
• Active trophoblastic disease
• Pelvic Inflammatory Disease
• Marked immunosuppression
• Current deep vein thrombosis or PE
• Ischaemic heart disease
• Active viral hepatitis, severe decompensated cirrhosis, benign liver tumours or malignant hepatomas
• Breast cancer within last 5 years

Altered patterns of menstrual bleeding

Up to 60% women stop using the LNG-IUS within 5 years - most common reason is unacceptable vaginal bleeding. Prior to commencing use of the IUS, women should be counselled that altered patterns of menstrual bleeding are common - irregular bleeding and spotting (common in the first six months of treatment) and amenorrhoea in particular. Amenorrhoea is reported in 65% of women using the LNG-IUS after 1 year and is perceived by many as a benefit.^4,5

Hormonal symptoms

Acne, headaches, breast tenderness and nausea are reported by LNG-IUS users but in a systematic review these do not differ significantly from IUCD users. Serum LNG levels with an IUS are lower than with oral or subdermal administration of progestogen but there is wide individual difference, possibly explaining the variation in experience of hormonal side-effects.

Ectopic pregnancy

Overall rates are lower than with no contraception. However, if a woman does become pregnant with a LNG-IUS in situ, the risk of an ectopic is 1 in 20 so she should seek medical advice to exclude it. The risk of ectopic pregnancy is similar for LNG-IUS and modern IUCDs.⁵

Uterine perforation

Risk is small (1-2 in 1000) but significantly increased in lactating women.^5,17

Ovarian cysts

Functional, usually asymptomatic ovarian cysts are relatively common and usually resolve spontaneously. Consider ovarian pathology in IUS-users and if found, ultrasound monitoring is suggested.

Pelvic infection

There is a small increase in the risk of pelvic infection which occurs in the 20 days following the insertion of an LNG-IUS. Thereafter the risk of infection is the same as those not using the device.

Counselling

Prior to giving informed consent, women should be given verbal and written information including:

• Mode of action
• Duration of action: the LNG-IUS is effective for contraception and the treatment of menorrhagia for 5 years. Where women are aged 45 or over when their LNG-IUS is inserted and are amenorrhoea may keep it until they no longer need contraception even though this is beyond the licensed use and should be discussed with the patient and documented in the notes. Where the LNG-IUS is providing endometrial protection during oestrogen replacement therapy, it can only be assumed to be effective for 4 years.
• Contraceptive efficacy and failure rate
• Reversibility and return of fertility
• No protection against STIs (safe sex and condom use should be promoted)
• Side-effects and risks
• Usual bleeding patterns
• When and how to seek help

Screening

Sexually Transmitted Infections (STI)

Prior to inserting a LNG-IUS, women who are at increased risk of STIs should be screened for Chlamydia (and gonorrhoea in areas of prevalence). Increased risk is associated with:

• Age under 25 years
• More than 1 sexual partner in the last 12 months
• A previous STI or current symptoms of infection

Nullips are not at increased risk of infection per se but the potential consequences of a pelvic infection may be of greater significance and this should be discussed with the patient. Where testing is not complete, prophylactic antibiotics should be given to women at increased risk of STIs prior to LNG-IUS insertion. Women may use the LNG-IUS within 3 months of treated pelvic infection provided they are symptom free.⁵

Endometrial abnormalities

Endometrial biopsy or ultrasound is not routinely required prior to LNG-IUS insertion for menorrhagia.⁵

Timing

• Ideally the LNG-IUS should be fitted within the first 7 days of a period and is effective immediately.⁵
• If fitted beyond 7 days, the risk of a pregnancy since the last period must be excluded prior to insertion and additional contraceptive precautions should be used for the next 7 days.
• The LNG-IUS can be fitted 6 weeks after a vaginal or caesarian section delivery.
• The LNG-IUS can be fitted immediately after a first-trimester abortion or miscarriage with immediate effect.

Fitting

• Only staff trained and up-to-date in fitting IUCDs should perform IUS-insertion. Insertion is commonly undertaken in general practice (as an enhanced service) or within the context of family planning or gynaecology clinics.
• For LNG-IUS insertion technique - see IUCD insertion technique.
• Women with cardiac valve defects should receive antibiotic prophylaxis at the time of fitting (and removal)

Follow-up and Problems

• Routinely 3-6 weeks after fitting or after first period to check threads and exclude infection or perforation.
• Further follow up should be driven by problems or when removal is desired or necessary.
• Bleeding: irregular bleeding and spotting is common in the first six months with a LNG-IUS. Where bleeding is not improving, refer at 6 months, or if menstrual flooding remove the LNG-IUS as the device's mechanical presence may be the cause. A new bleeding pattern in a woman previously with amenorrhoea or a stable bleeding pattern may indicate STIs, device displacement, pregnancy, endometrial polyps, hyperplasia or cancer and should be investigated fully.⁵
• Lost threads: see IUCD lost threads
• Presence of actinomyces-like organisms: often found coincidentally on cervical smear and should trigger an assessment for pelvic infection and removal of the IUS if signs of infection are present.
• Pregnancy: if a woman becomes pregnant with the IUS in situ, the IUS should be removed before 12 weeks gestation.

• Where pregnancy is desired, the LNG-IUS can be removed at any time.⁵
• If pregnancy is not desired, the LNG-IUS should be removed with menstruation or if no unprotected sexual intercourse in the previous 7 days, at other times.
• Where the LNG-IUS is to be exchanged, intercourse should be avoided for the previous 7 days in case reinsertion fails.
• When switching to the combined oral contraceptive, remove after 7 consecutive pills.
• When switching to the progesterone only pill, remove after 2 consecutive pills.
• When switching to the depot or implant progestogen methods, remove the LNG-IUS after 7 days of use of the new method.

• The LNG-IUS (and other long-acting reversible contraceptives) is more cost-effective than the combined oral contraceptive pill even at one year of use.⁴
• It is also more cost effective than injectable contraceptives.
• In the past, doctors have been reluctant to fit LNG-IUS devices on the basis of item cost but cost-effectiveness analyses show this to be a false saving when other costs are taken into account.