Most people can safely use an IUD, but in some cases, side effects or complications are more likely. Talk to your nurse or doctor to find out if an IUD is safe for you. You may not be able to get an IUD if you have: - Certain sexually transmitted diseases or pelvic infections - Think you might be pregnant - Untreated cervical cancer - Uterine cancer - If you have had a pelvic infection in the last 3 months after labour or miscarriage You also should not use the Paragard IUD if you have a copper allergy, Wilson's disease, or a bleeding disorder that makes it harder for blood to clot. You should not use an IUD if you have breast cancer. Rarely, the size or shape of a person's uterus can make it difficult to place an IUD properly. If you are not medically able to fit an IUD for you, don't worry. You also have many other birth control options.