How effective is it?
Over 99 per cent effective. Less than one woman in 100 will get pregnant in a year. Older IUDs have less copper and are less effective.
How does it work?
A small plastic and copper device is put into the uterus. It stops sperm reaching an egg, and may also stop a fertilised egg implanting in the uterus.
What are the advantages?
Works as soon as it is put in.
Can stay in 5–10 years depending on type, but can be taken out at any time.
You don’t have to think about contraception for as long as the IUD is in place.
When the IUD is removed your fertility will return to normal.
What are the disadvantages?
May not be suitable for women at risk of getting a sexually transmitted infection.
Periods may be heavier or longer and more painful.
Very small chance of getting an infection during the first 20 days after insertion.
A small increased risk of ectopic pregnancy if the IUD fails.
Anything else I should know?
If fitted after 40 it can stay in place until the menopause.
Women are taught to check the IUD is in place by feeling the threads high in their vagina.
A check for any existing infection is usually advised before an IUD is put in.
Not affected by other medicines.