Unplanned pregnancy. Coloured 3-D ultrasound scan of an embryo (brown, upper centre) developing in the uterus despite the presence of an intrauterine device (IUD, white, upper left). An IUD is a small coil of plastic or wire that is placed in the uterus to prevent an embryo from implanting in the uterine wall. The failure rate of IUDs is around 2-3 percent. If no abortion is planned, then the IUD should be removed. Otherwise, there is an increased chance of a miscarriage or premature birth. However, if the IUD cannot be removed, the pregnancy often proceeds to full-term, and the IUD does not harm the baby. This scan was taken after 7 weeks of pregnancy.