The Mirena® intrauterine contraceptive device (IUD) or LNG-IUD is a small, t-shaped device which is fitted inside the uterus, where it releases a hormone to prevent pregnancy
What is Mirena®?
Mirena® is the brand name for the Levonorgestrel IUD (LNG-IUD).
It is a T-shaped device, made of plastic with two fine nylon strings attached. The IUD sits in the uterus and the strings come through the cervix and sit against the wall of the upper vagina. Once in place you cannot feel the IUD in the uterus. You can feel inside the vagina to check these strings that tell you that the IUD is in place. The strings are also used to remove the IUD.
How does Mirena® work?
The long arm of the Mirena® is covered by a fine membrane. This contains progestogen (a hormone similar to the hormone progesterone which is naturally produced by the female body). Progesterone prevents a pregnancy for up to 5 years by steadily releasing small amounts of the progestogen directly into the uterus. The effect of the hormone is to:
- thicken the mucus in the cervical canal to prevent sperm entering the uterus
- change the lining of the uterus, making it unsuitable for pregnancy
What are the advantages of Mirena® as a method of contraception?
- highly effective
- long-acting (effective for 5 years)
- reversible and fertility returns within a month
- reduces amount of blood loss with periods
- reduces period and pelvic pain
- does not interfere with breastfeeding
- cost effective over 5 years
Who can use a Mirena®?
There are very few contraindications to a Mirena® and it suits most women. Mirena® may be particularly suitable for women who:
- wish to use an effective long-term but reversible method of contraception
- have difficulty remembering to take a pill
- want to reliably space their family
- have completed their family
- have heavy, painful periods
- are unable to take oestrogen
- are approaching menopause
Who should not use a Mirena®?
Mirena® may not be suitable for women who have:
- unexplained vaginal bleeding (this should be investigated before using a Mirena®)
- a recent history of PID (pelvic infection)
- uterine or cervix abnormalities
- have difficulties with vaginal examinations and procedures
Mirena® is not suitable for women who have recently had breast cancer or some other forms of cancer.
What are the disadvantages of Mirena® as a method of contraception?
- insertion and removal of the device requires a procedure that is a little uncomfortable and can only be performed by a trained doctor or nurse
- after the insertion there may be irregular light spotting for 2 weeks to 6 months while the IUD settles in. After this most women have light regular periods, no periods, or infrequent bleeding. Uncommonly, the bleeding may be unacceptable to some women
- does not protect against sexually transmitted infections (STIs)
What are the possible health benefits of Mirena®?
- It can be used to treat excessively heavy menstrual bleeding once serious causes for heavy bleeding have been investigated by a doctor
- For women 45 years or over, the IUD can be left in for 7 years – until after the menopause (this will be checked by our doctor performing two hormone tests 6 weeks apart).
- For women using estrogen for menopausal symptoms who have not had a hysterectomy, the IUD can be used as the progesterone component of HRT to balance the estrogen effect on the uterus.
When can a Mirena® be inserted?
- For women having periods a Mirena® is best inserted on the first week that the period starts.
- After a baby, for women who are not breast feeding, anytime provided a pregnancy is excluded
- For women who are breast feeding, any time
How can I get a Mirena®?
A trained doctor will assess you by:
- Asking you questions about your reproductive, sexual, and medical health
- Check that your Pap tests are up to date
- Possibly test for infection
- Ask if you tend to faint easily
- Provide you with a prescription for the Mirena®
You will be asked to return with the Mirena®, that day or another time, for insertion according to the best time for you.
It is a good idea to have something to eat before coming to the clinic.
The procedure takes about 10 minutes. Most women find the procedure a little uncomfortable, some women find it painful.
For the insertion, sometimes a local anaesthetic is given into the cervix. Occasionally a woman may prefer or need to have the insertion as a day case in a hospital while asleep.
Occasionally some women feel faint during or after the procedure. After insertion you will be asked to rest at the clinic for 10-15 minutes before you leave.
Following insertion, some women notice bleeding or abdominal cramping overnight or for a few days.
You should expect light intermittent spotting from 2 weeks to 6 months while the IUD settles in.
A follow up visit will be made for 3-4 weeks to check on the placement and the bleeding pattern.
What are the possible side effects of Mirena®?
With a Mirena®, a very small amount of progestogen passes into the bloodstream. This means that side effects are fairly rare, mild and often improve with time. They include acne, breast soreness, headache and mood changes. Mirena® should have no effect on weight.
Complications of the insertion procedure can include:
perforation - This is a rare but potentially serious complication where the Mirena® device passes through the wall of the uterus into the pelvic area, usually at the time of insertion but can very occasionally occur later. This can occur in about one per 1000 insertions. This requires surgery under a general anaesthetic to remove the Mirena®.
expulsion - Sometimes the Mirena® device may be partially or completely pushed out by the uterus. It occurs in about 5 per 100 insertions. It is important to check for the threads after each period in the first few months after insertion.
infection - Pelvic inflammatory disease (PID) The risk of PID is also related to exposure to sexually transmitted bacteria (chlamydia and gonorrhoea). It is most often seen in the first 3 weeks after insertion due to an existing infection. It is important that you consider carefully your potential risk of acquiring an STI throughout the whole period of time you have the Mirena® device in place. PID may in some cases lead to infertility.
pregnancy - The chance of pregnancy is 1 in 1,000. In the rare event of a pregnancy with a Mirena® in the uterus there is a small risk of a miscarriage or ectopic pregnancy (a pregnancy outside the uterus – most often in the Fallopian /uterine tube). This is an uncommon complication and less common than amongst women who are not using any contraception. An ectopic pregnancy may present with abdominal pain or bleeding.
What else do I need to know about the ongoing use of Mirena®?
The Mirena® needs to be replaced with a new device every 5 years to work effectively.
Find an event that will remind you of this, for example a significant birthday.
The Mirena® can be removed before this date for any reason but it is important to arrange another method of contraception before the device is removed as fertility can return immediately after removal.