It works for five years. It doesn't interfere with sex. After you have used an IUS for about three months or so your periods usually become much lighter and shorter, so an IUS can be useful if you usually have very heavy, painful periods. An IUS usually reduces or gets rid of period pain. Your usual fertility returns quickly when the IUS is removed.
Most women have slight irregular bleeding between their periods, for the first three months or so.
This can be annoying, but should settle down. You may get temporary side-effects such as headaches, acne and breast tenderness. If you do get any of these they usually go away after a few months. Some women may have cysts on their ovaries in the first few months. These are not dangerous and do not usually need to be treated.