The IntraUterine System or IUS is an IntraUterine Device (IUD or "coil") that has a hormone cylinder that releases levonorgestrel (a progestogen or progestin) on its shaft, rather than the traditional copper wire. The brand available in the UK, US and Canada is Mirena® coil made by Schering Health.

Clinical uses

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The progestogen helps reduce endometrial build up and so lightens periods and gives rise to its two licensed uses:

• As a contraceptive, particularly suitable for those with very heavy menses.
• As a treatment for menorrhagia (heavy periods) for women who might previously have required a hysterectomy.

The IUS, unlike IUDs, is not licensed for use as an Emergency contraception (Manufacturer states the progestogen, unlike copper, is not deleterious to the developing embryo).

The IUS, like the IUD is thought to be more suitable for women who have already had children as they will find dilating the cervix less uncomfortable. Doctors more experienced in fitting coils, such as Family Planning doctors rather than GPs, are usually more willing to consider women who have never given birth.

The IUS is not suitable as a method of safe sex, though it is a very effective contraceptive. It is therefore most suitable for women in long-term relationships without a high risk of STDs.

Fitting

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The IUS can only be fitted by a doctor. The device should be inserted according to the manufacturer's instructions using aseptic technique to avoid adverse events.

The process of opening the cervix (both to measure the uterus and insert the IUS) is uncomfortable and some women will even describe it as painful. Doctors often advise women to take painkillers before the procedure to reduce discomfort.

Once in place, the IUS will give reliable birth control for 5 years.

Benefits

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• Lighter periods, which in a third of cases will stop alltogether (amenorrhea).
• Fewer family planning appointments - women with an IUS only need to see a doctor once a year for a quick check up.
• The localised release of the progestin (or progestogen) into the uterus results in less systemic side effects compared to Progesterone only pill or Depo Provera.
• Will not interfere with sex.
• Unlike the pill, it can be forgotten (apart from needing a replacement after 5 years).
• After the IUS is removed, normal fertility returns quickly.
• Over 99% effectiveness.

Disadvantages

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During fitting:

• perforation of the uterus or cervix during insertion.
• sepsis, though risk may be reduced by proper aseptic technique during insertion.

For up to three months after fitting:

• Periods can become irregular
• irregular bleeding
• Headaches.
• Breast tenderness (mastalgia)

However, these side effects should be temporary and disappear within three months.

Rare but serious adverse reactions include:

• ectopic pregnancy.
• intrauterine pregnancy (small risk miscarriage and bleeding, but likewise if attempted removal).
• Pelvic inflammatory disease - usually associated with sexually-transmitted infections.
• embedment of the device in the myometrium.
• ovarian cysts (usually not dangerous, and rarely require treatment).
• breast cancer.

Hence, the device is contraindicated in patients who may be at increased risk for these reactions. More information regarding warnings, contraindications, and other adverse reactions may be found at the manufacturer's website.

References

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• Continuous Identification of Research Evidence (collaborative of the WHO, and US CDC & Johns Hopkins Hospital) - Search of Evidence about the IUS

Hormonal contraception | Intrauterine contraception