IUD is short for intrauterine device, a widely used method of birth control. It’s a small plastic device wound with copper wire.
An IUD is inserted into the uterus by a physician. It slows down the motility of the sperm, preventing it to reach an ovum, and changes the lining of the uterus to prevent implantation if an egg is fertilized.
It’s effective as soon as it is placed.
The reliability is high, but not 100%. Of 100 women using an IUD for a year 1 or 2 will become pregnant. But it’s definitely more effective in preventing pregnancy than a condom. When 100 couples use only condoms for a year 2-12 will become pregnant.
An IUD does not protect you against STD’s. So if your boyfriend (might have) had unsafe sex, you better use both an IUD and a condom. Then you are very well protected.

How does the IUD work?
Advantages
Disadvantages