Is it true that iuds can cause infections and cancer?

No: The IUD should not be placed if you have an active infection or are at high risk of developing an infection (ie, multiple sexual partners, no condom use), but the device itself does not cause infection. In addition, it does not cause cancer and may actually be used to treat endometrial hyperplasia (increased thickness of the uterine lining that may be a pre-cancerous condition).

IUDs and Cancer : A recent lancet study found that a large number of women surveyed had a 44% reduced risk of developing cervical cancer, presumably by interfering with the hpv virus. Endometrial cancer risk is also reduced. Most infections that develop have been found to be due to stds or non-sterile device insertion. In summary, iuds are enjoying a renaissance among birth control methods and are safe for most.