Mirena has drastically changed the way we practice modern gynaecology. This little T-shaped plastic device not only provides reliable and fully reversible contraception; it alleviates much of the suffering of women who have heavy periods.

Many patients in our gynaecology clinic have heard about Mirena: many patients will mention a friend or family member who tried Mirena in the past. Each presentation is unique, and it is important to understand the full spectrum, to be certain it is a good option for you.

Mirena basics

What is a Mirena IUD?

As you can see from the photo on the rig, Mirena is a small T-shaped plastic device. It is inserted inside the uterine cavity, and contains 52mg of levonorgetrel hormone. Levonorgestrel is a synthetic version of the hormone progesterone (which is made naturally by your ovaries). Mirena has a coating that controls the slow release of this hormone (20 mcg/daily) into the uterine lining.

Mirena has two fine nylon strings attached to it. When the Mirena IUD is in place, the strings come out through the cervix (the neck of the uterus) into the top of the vagina. Strings allow easy removal of the device, which can be performed by any doctor or trained nurse practitioner who can perform a speculum examination.

How does a Mirena work?

Mirena has both contraceptive and therapeutic effects. We can discuss these separately:

Contraceptive

• All IUD’s affect the way sperm move and survive in the uterus, stopping sperm from meeting the egg
• The hormonal IUD’s such as Mirena and Kyleena make the mucus in the cervix thicker, so that sperm cannot get into the uterus
• Mirena IUDs thin the inner lining of the uterus (the ‘endometrium’), which makes the environment hostile for a fertilised egg to implant
• Sometimes, the Mirena IUD prevents your ovaries from releasing an egg (ie. stops ovulation)

Therapeutic

• Mirena IUDs thin the lining of the uterus (the ‘endometrium’), which makes periods lighter and / or shorter, or sometimes even stops periods all together
• Lightening of periods often leads to less painful periods
• May slow the growth of endometriosis
• Protection from endometrial hyperplasia (excessive growth of the lining of the uterus) during menopausal hormonal therapy

How long can a Mirena stay in for?

Mirena lasts 5 years, but even after that time it doesn’t “expire” immediately: Mirena continues to produce hormones, but at half the rate. Hence, we do recommend Mirena is changed every 5 years.

However, if Mirena is inserted at the age of 45 years old (or later), it can be left in for 10 years.

Potential benefits of Mirena IUD

Mirena has many benefits, which will be outlined below.

Lighter periods

Most women find that their periods are significantly lighter with a Mirena IUD in: some women stop having periods all together. This is absolutely safe for your body, to have a break. However, in the process of making your periods lighter, Mirena can cause unpredictable spotting in the first 3 – 6 months after it is inserted. This is because Mirena thins the lining of the uterus, which can become a little unstable and shed, causing irregular light bleeding.

I often suggest that my patients give Mirena a chance, so they can fall in love with it. If needed, some clinicians add in oral contraceptive pill during the first few months of Mirena use, to provide some control over the bleeding pattern.

However, if your bleeding pattern remains unacceptable after 6 months of use, Mirena may not be the best option for you: chat with your gynaecologist to explore other options.

In 20% of women who use Mirena, periods will stop in the first year of insertion. It is recommended that you do a pregnancy test if your period is delayed by 2 weeks, just in case you’re the 1 in 1,000 women who conceive with a Mirena in. Once pregnancy has been ruled out, repeated pregnancy tests are generally not necessary.

If you are using Mirena with estrogen replacement therapy (such as an estrogen menopausal hormonal therapy patch), a non-bleeding pattern is likely to develop during the first year of use.

Contraception

Mirena is considered extremely reliable contraception, with a quoted effectiveness rate of 99.9%. Keep in mind that (short of a hysterectomy), no contraceptive options are 100% effective: even gettings your tubes tied has a small rate of unplanned pregnancy thereafter.

One big advantage of Mirena is that you don’t need to remember to take a pill every day: I like to think about it as a “fit and forget” option. It’s also very cost-effective, in that it provides five years of contraception. Once your Mirena IUD is removed, your fertility returns within 4 – 6 weeks.

Mirena is a very private form of contraception, in that your partner doesn’t need to know that it is in place.

Safe to use if breastfeeding, or you can’t take oestrogens

Mirena is safe to use while breastfeeding. We can insert Mirena at the time of Caesarean section, or immediately after vaginal birth, but there is a slightly higher chance of the Mirena falling out (as your uterus may be large, and bleeding is heavier immediately after birth). Most women choose to have their Mirena inserted 6 – 12 weeks after their baby’s birth, which is the recommended time. Just remember: fertility can return as early as 25 days post-birth, so alternative contraception  (such as condoms) should be used up until your Mirena is inserted.

For some women, it’s not safe to take oestrogen-containing medications, such as the combined oral contraceptive pill. (Examples of conditions that preclude oestrogen include: migraines with visual aura; high, uncontrolled blood pressure; acute liver disease; and previous venous thromboembolism.) Because Mirena doesn’t contain any oestrogen, it is safe in the presence of these conditions.

Fertility returns quickly

Mirena has no effect on your fertility after it is removed, and can be used in women who have never been pregnant before. It’s also suitable for teenagers. Fertility returns almost immediately upon removal of the device.

Potential drawbacks of Mirena IUD

As with any medical treatments there are some potential risks, that you need to be aware of.

Risk of infection

There is a small (0.3%) increased risk of pelvic infection during the first 20 days after insertion. It is often related to an asymptomatic and unrecognised sexually transmitted infection (STI). To reduce this risk, your doctor may recommend STI testing before inserting your Mirena.

The good news is that after the first 20 days, the rate of pelvic infection in IUD users is approximately the same as would be expected in the general population, who don’t have an IUD in, which is very low!

Risk of expulsion

There is a very small risk that the IUD will fall out, or be expelled. The IUD is most likely to fall out during the first few months, most often during your period. If you think your IUD might have moved or fallen out, use a back-up method of contraception (such as condoms) until you can see a doctor.

Some women will be comfortable performing a self-check to see if the IUD string ends can be felt within vagina. This can be done monthly after your period ends.

Risk of perforation

A perforation is a small hole in the wall of the uterus which is created during IUD insertion. As a result, the IUD can move through the hole and sit in the wrong place (such as in amongst your pelvic organs). In this case you will need keyhole surgery to remove your IUD. Luckily, risk of perforation is very low: approximately once every 1,300 Mirenas.

You may need a general anaesthetic

Many women can tolerate insertion of Mirena in the the clinic, without needing any anaesthetic. Most women rate pain during insertion 4 – 6 out of 10, with 10 being the worst pain they can imagine. Generally speaking, women who have never given birth vaginallly feel more discomfort than women who have. Even though, sometimes passing the instrument through the cervix can be too uncomfortable. In these cases, the doctor would stop and organise insertion on another day with general anaesthetic, when you are fully asleep.

Some women choose to have their Mirena inserted under general anaesthetic (without trying an awake procedure), which is a valid choice!

Possible progestogenic side-effects

If you read the Mirena leaflet, you will see a list of progestogenic side-effects. Remember it doesn’t mean they will all happen to you: many of them are rare.

Mirena may cause a slight increase in the likelihood of: vaginal dryness; flushing; headache; breast tenderness; nausea; mood swings / depression; abdominal discomfort; and acne.

Some of these side-effects will settle with time. Of note, Mirena IUD has not been shown to cause weight gain.

What is involved in having an IUD inserted?

Inserting a Mirena only takes about 15 minutes. It involves:

• Performing a urine pregnancy test
• Positioning in a gynaecological examination chair
• A speculum examination. (This is a good opportunity to catch up on cervical screening test, if you are due for one.) Once the doctor can see your cervix, they will clean the cervix with an antiseptic solution.
• Local anaesthetic spray or injection can be used.
• The cervix is grasped, then a thin instrument is passed through the cervix to measure the length of the uterus
• The Mirena IUD can then be inserted through the cervix, and the strings cut

You are likely to feel pelvic cramps when any surgical instruments are passed through the cervix; some women feel a bit light-headed. Make sure you’re feeling OK before you stand up and get dressed.

It is important that you do not have intercourse or use tampons for 48 hours following insertion, to decrease the risk of infection.

Taking paracetamol or ibuprofen 30 minutes prior to insertion may help reduce pelvic cramps during and after Mirena insertion. Simple pain relief may be needed for the 24 – 48 hours following insertion. If possible, try to time it so that your Mirena is inserted when you have your period, as your cervix will be slighty open, and the procedure less painful.

Frequently asked questions (FAQs)

How much does a Mirena cost?

It varies between pharmacies, but Mirena costs around $40 if you have a Medicare card. For people who have a healthcare card, the out-of-pocket cost of a Mirena is only $6.

If you don’t have Medicare card, Mirena will cost you approximately $200. Keep in mind that the Mirena provides five years of contraception, so even this higher cost averages out to less than $1 per week of contraception.

How is a Kyleena different from a Mirena?

Both Mirena and Kyleena are very effective methods of contraception. Mirena is 99.9% effective and Kyleena is 99.7% effective.

Kyleena is slightly smaller than Mirena (30mm long and 28mm wide for Kyleena, compared to 32mm long and 32mm wide for Mirena). Some younger women may prefer to try Kyleena for contraception, due to its smaller size.

Kyleena has a lower dose of the hormone (19.5mg for Kyleena, compared to 52mg for Mirena), but is less effective than Mirena at lightening periods.

As gynaecologists, we recommend using Mirena (rather than Kyleena) to treat heavy periods, endometriosis or as a part of menopausal hormonal therapy.

Are there any conditions in which it’s not safe to have an IUD?

• Current pregnancy (for obvious reasons)
• Acute pelvic infection, as insertion of device can worsen the infection
• Personal history of breast cancer
• If your uterus is an unusual shape, or you have large fibroids distorting your uterine cavity. For some patients, Mirena can still be used, but only after correcting the shape of the uterine cavity.

Do IUDs prevent sexually transmitted infections (STIs)?

Mirena doesn’t prevent STIs. So if you are concerned about preventing an STI, you’ll need to use condoms when having penetrative sex, even if you have a Mirena in.

Conclusion

Mirena is a long-acting and fully reversible contraceptive device, which can also be used for the treatment of heavy menstrual bleeding, endometriosis, and as a part of menopausal hormonal therapy.

Mirena works really well in these situations, and is generally well tolerated, but it does need time to settle in! So please persist for the first few months, and your Mirena is likely to repay your loyalty in spades.