Family doctor


Women's Health

THE MIRENA IUD - a patient's guide


The Mirena is a new contraceptive. It is an IUD which releases a progestogen hormone to stop conception and help reduce heavy periods. This article looks the benefits and possible side effects.


  • Mirena is an IUD (intra-uterine device) which also releases a low dose of the hormone levonorgestrel (a progestogen hormone)
  • A significant advantage of Mirena is that it usually reduces blood loss during menstruation by up to 75 percent
  • It can also be used to control very heavy periods (menorrhagia), provided there is no underlying serious cause. Used in this way it may be a useful alternative to hysterectomy for certain women.
  • Mirena is nearly 100 percent effective at preventing pregnancy
  • It should be inserted within 7 days of the first day of a period. Screening for sexually transmitted diseases should be done prior to insertion
  • The IUD should be changed after 5 years
  • Menstrual problems (usually spotting) are the most commonly reported side effect particularly in the early months

What is it?

Mirena is a new development in the contraceptive market. It is an IUS (intrauterine system) which slowly releases a progestogen hormone (levonorgestrel). This is one of the main normal female hormones produced by the ovaries and also present in the combined contraceptive pill and in the mini-pill (progestogen only pill). It is also present in some forms of hormone replacement.

Mirena is a small T-shaped device which contains a total of 52 mg levonorgestrel with a release rate of 15 Ug per 24 hours.

The low-dose hormone works as a contraceptive by its effects on the lining of the uterus and also making the cervical mucous more hostile. Ovulation may be inhibited in some women, but this is not the main mechanism of action.

The ovaries continue to function normally (producing the female hormone estradiol, even when periods become absent (as happens in approximately 20% of users).

There is a failure rate of 0.16 per 100 women years of use. This is similar to tubal ligation or vasectomy.

The ectopic pregnancy rate is also low at 0.05 per 100 women years (compared to 1.2 to 1.6 for women using no contraception).

Unlike other IUDs, the Mirena decreases the amount of blood lost during menstruation. Conventional IUDs can increase period flow by about 50 percent, whereas Mirena decreases blood loss by 75 percent.

It may be used as a treatment in women with very heavy periods, provided underlying pathology has been excluded first. It may decrease blood loss by up to 88% in this situation and can be a useful alternative to hysterectomy in certain situations.

Periods become lighter and more infrequent six months after insertion and studies have found it decreases blood loss by up to 97 percent after one year. Mirena also helps to ease painful periods (dysmenorrhoea).

Mirena cannot be used as a form of emergency contraception like copper IUDs can.

Studies show Mirena does not interfere with future fertility. Around 80 percent of the women who wanted to become pregnant conceived within 12 months after the IUD was removed.

How is it inserted?

An appointment to check for infection, examine the cervix and make sure a recent cervical smear has been performed is usually done before it is inserted.

The IUD should be inserted during period time and a non steroidal anti-inflammatory taken 2 hours prior to the appointment. The device should not be inserted until six weeks after child birth.

A local anaesthetic may be needed in women who have not had children before.

Follow up care:

A follow up appointment should be made within two weeks to check the IUD. You will be asked about bleeding patterns, pain, discharge, and undergo a pelvic examination.

A three monthly check may also be required to discuss the above symptoms, followed by annual check ups after that.

Mirena should be removed or changed after five years.

It is removed by gently pulling on the threads with forceps. Removal is best carried out during menstruation. If it is removed during mid-cycle and the woman has had sex within the week, she is at risk of pregnancy unless a new device is inserted.

Side effects

There can be some spotting during the first months of use, and menstrual problems are the most commonly reported side effects.

Some women stop getting periods altogether in the months following the insertion of Mirena. Other changes in bleeding patterns include shorter or longer menstrual periods, heavy flow and painful periods. Any concerns should be discussed with the doctor who inserted it.

Other reported problems include headache, lower abdominal pain, back pain, skin disorders, vaginal discharge, benign breast problems, vaginitis, depression, mood changes, nausea. Other isolated side effects reported included weight gain, hair loss, greasy hair, increase in hair growth (hirsutism). These are rare side effects and need to be balanced against the advantages of good worry-free contraception which is reversible.

There is a risk of pelvic infection from using Mirena but studies suggest the risk is lower with this system than copper IUDs. There is a higher risk of pelvic infections with multiple sexual partners.

The device can be fully or partially expelled from the uterus, and symptoms of this can include bleeding or pain. However, some women experience no symptoms with expulsion.

Very rarely, the cervix or uterine corpus can be perforated during insertion.

There is also a low risk of ectopic pregnancy. Women with lower pelvic pain in conjunction with missed periods should seek medical advice.

A condition known as "delayed follicular artresia" can occur in rare cases. In these cases the release of egg follicles is delayed and the follicles continue to grow and they cannot be distinguished from ovarian cysts. Some can cause pelvic pain and rarely surgery is required.

It is possible for the threads on the device to become lost. Pregnancy must be excluded in this case. It is possible for them to be drawn up into the uterus and for them to reappear during the next period. If they are not found, the device may have come out. An ultrasound may be necessary to determine this.

Who should not use Mirena?

The device cannot be used by pregnant women or those with pelvic inflammatory disease, lower genital tract infections, cervical dysplasia, uterine or cervical cancer, undiagnosed abnormal bleeding, fibroids which distort the uterus, severe liver disease, or allergies to the ingredients in the device.

The system should be used with caution in women with a history of migraine, jaundice, high blood pressure, diagnosed or suspected hormone dependent cancer such as breast cancer, leukaemia, blood clots (venous or arterial thrombosis), stroke, heart attack, congenital heart disease, or valvular heart disease.

Low-dose levonorgestrel may affect glucose tolerance in women with diabetes and blood glucose should be monitored.

Getting help

Your doctor, gynaecologist or local Family Planning Clinic will be able discuss the Mirena with you and arrange insertion if needed.

See also:

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