IUCDs are not suitable for all women. Using them carries the following risks:

• Pelvic inflammatory disease (PID): One of the main concerns about using IUCDs is the possibility of developing PID. Both using an IUCD and being at high risk of acquiring sexually transmitted infections (STIs) make women more likely to develop PID. The greatest risk of pelvic infection associated with the use of IUCDs occurs at insertion. This increased risk of infection may be associated with a microbiological contamination of the endometrial cavity at that time.
• Human immunodeficiency virus (HIV): Whether IUCDs increase the risk of acquiring HIV is not known. The effect of IUCDs on the uterine lining may create an environment favourable to HIV transmission. It is possible that the increased bleeding associated with the use of some IUCDs may increase the transmission of the virus from HIV-positive women to their partners.
• Menstrual problems: Increased menstrual pain (dysmenorrhoea) may accompany IUCD use. Between 10%–15% of IUCD users have their IUCD removed because of symptoms or signs associated with bleeding or spotting. However, the amount of blood is usually minor and of little consequence.
• Expulsions: An IUCD may come out of the uterus, possibly without the woman knowing. This is more common when the IUCD is inserted soon after childbirth, or when there are abnormal amounts of menstrual flow or severe dysmenorrhoea (painful cramps during menstruation).
• Pregnancy: Half of intrauterine pregnancies that occur with the IUCD in place end in spontaneous abortion. If the IUCD is removed early in pregnancy, the spontaneous abortion rate drops to about 25%. Leaving the IUCD in place during pregnancy increases the risk that the mother will have severe pelvic infection that could lead to her death. About 5% of women who become pregnant with an IUCD in place will have an ectopic pregnancy.