A mechanical device, commonly a coil, inserted into the UTERUS to prevent CONCEPTION, probably by interfering with the implantation of the EMBRYO. For many women, IUCDs are an effective and acceptable form of contraception, although only about 10 per cent of women in the UK use them. The devices are of various shapes and made of plastic or copper; most have a string that passes through the cervix and rests in the vagina.

About one-third of women have adverse effects as the result of IUCD use: common ones are backache and heavy menstrual bleeding (see MENSTRUATION). The frequency of unwanted pregnancies is about 2 per 100 women-years of use. (See CONTRACEPTION.)