NHS Choices - Risks
Complications after having an IUD fitted are rare. Most complications will appear within the first year after fitting.
Longer or heavier periods can be a side effect of the IUD (particularly if you've always had heavy periods). For some people, this eases within a few months, but others continue to have longer and heavier periods.
If the problems continue, you may wish to consider an intrauterine system (IUS), which releases hormones that can reduce bleeding and pain.
The most common reasons for women having their IUD removed are vaginal pain and bleeding.
Pelvic infections can occur in the first 20 days after the IUD is fitted. The risk of infection from an IUD is extremely small. Less than one in 100 women who are at low risk of sexually transmitted infections (STIs) will get a pelvic infection.
Your GP or clinician will usually recommend an internal examination before fitting an IUD to check that there are no existing infections.
See your GP or clinician immediately if you get any pain in your lower abdomen or have a high temperature or smelly discharge in the first three weeks after your IUD is fitted. This may be pelvic inflammatory disease (PID), which can lead to infertility.
Occasionally the IUD is rejected by the womb (expulsion) or can move (displacement). This is more likely to happen soon after it has been fitted, although this isn't common. Your GP or clinician will teach you how to check that your IUD is in place.
Damage to the womb
In very rare cases, an IUD can go through (perforate) the womb or neck of the womb (cervix) when it's put in. This can cause pain in the lower abdomen but doesn't usually cause any other symptoms. If the GP or clinician fitting your IUD is experienced, the risk of this happening is extremely low.
If perforation occurs, you may need surgery to remove the IUD. Contact your GP immediately if you feel a lot of pain after having an IUD fitted as perforations should be treated straight away.
If the contraception fails and you become pregnant, your IUD should be removed as soon as possible if you're continuing with the pregnancy.
There's a small increased risk of ectopic pregnancy if a woman becomes pregnant while using an IUD.