The intrauterine system (IUS)
The intrauterine system (IUS) (also known as the “Mirena”) is a small T-shaped plastic device that is fitted in the uterus (womb). It provides contraceptive protection for up to five years.
The IUS steadily releases small amounts of a hormone called progestin which thickens the fluid around the neck of the uterus (stopping sperm from getting to an egg) and makes the lining of the uterus thinner so that a fertilised egg cannot grow. It also makes it harder for sperm to get into the uterus.
Inserting an IUS is a simple procedure that takes about 5 minutes. A trained person inserts the IUS through the vagina. The IUS sits in the uterus and does not move from there. There are threads attached to the IUS which sit in the vagina that assist with removal and allow you and your provider want to check the IUS is in the right place.
How good is the IUS at preventing a pregnancy?
- The IUS works very well at preventing pregnancy
- Less than 1 of 100 of people who use the IUS will become pregnant
What are the advantages of the IUS?
- Once in place, you don’t need to think about the IUS or do anything until it needs replacing, which can be up to five years, depending on the type of IUS you are using
- You can get the IUS removed whenever you want
- Your fertility will return to normal immediately after the IUS is removed
- The IUS is great if you have heavy or painful periods, as it usually makes periods lighter and less painful. Many users stop getting periods with the IUS. Lighter or no monthly bleeding is not harmful and will not affect future fertility
- The IUS can be inserted right after childbirth, abortion or miscarriage
- It is not used during sex so will not affect spontaneity. Neither you nor your partner should be aware of the IUS during sex
What are the disadvantages of the IUS?
- An IUS requires a vaginal examination and a simple, short procedure to fit it in the uterus (womb)
- The most common side effects of the IUS are lighter and fewer days of bleeding, or irregular bleeding. Many users stop having a monthly period. Irregular bleeding or spotting should settle within the first six months of use.
- A small number of users may experience other side effects due to the hormone in the IUS, such as acne, headaches, or breast tenderness. These usually settle down after the first few months of use.
- Condoms are the only contraceptive method which protect against sexually transmitted infections. To ensure protection from both pregnancy and infection, we recommend "dual protection". This means using a male or female condom in addition to the contraceptive method of your choice to prevent pregnancy.
How do I know the IUS is still in place?
It is rare for the IUS to fall out or move. Most women can self-examine and feel the small, very thin thread attached to the end of the IUS which comes out of the cervix and into the vagina. When you have the IUS inserted make sure your carer shows you how to find the thread so you feel confident to find it again.
What are the possible risks of using the IUS?
- There is a small risk of infection when the IUS is put in
- There’s a very small risk that the IUS might go through (perforate) your uterus (womb) or cervix when it’s put in. If it does happen, the IUS may have to be removed by surgery
- The IUS moves out of place or falls out and stops providing protection against pregnancy