How effective is it?
Over 99 per cent effective. Less than one woman in 100 will get pregnant over five years.
How does it work?
A small T-shaped plastic device is put into the uterus. It slowly releases the hormone progestogen. It thins the lining of the uterus to prevent a fertilized egg implanting. It also thickens the cervical mucus. This makes it difficult for sperm to meet an egg.
What are the advantages?
- Works for five years but can be taken out sooner.
- Periods usually become lighter, shorter and sometimes less painful or periods may stop altogether.
- You do not have to think about contraception for as long as the IUS is in place.
- When the IUS is removed your fertility will return to normal.
What are the disadvantages?
- Irregular bleeding or spotting is common in the first six months.
- Very small chance of getting an infection during the first 20 days after insertion.
- May get ovarian cysts.
- Insertion can be uncomfortable.
Anything else I should know?
- If fitted after 45 it can stay in place until the menopause.
- Women are taught to check the IUS is in place.
- Can be useful for women with very heavy and/or painful periods.
- A check for any existing infection is usually advised before an IUS is put in.
- Not affected by other medicine.