IUD contraceptive and sperm cells

IUD contraceptive and sperm cells. Computer artwork of an intrauterine device (IUD, red and white, centre) in a woman's uterus, surrounded by sperm cells (white, not to scale). The IUD is a contraceptive device that is implanted in the uterus to prevent pregnancy. It does not interfere with the sperm cells (male reproductive cells), one of which may fertilise an egg cell (female reproductive cell). However, when a fertilised egg tries to implant in the wall of the uterus, the shape and material of the IUD disrupts this process. This IUD has a coil (red), made of a metal such as copper. If the implantation fails, the fertilised egg is lost during menstruation. This view looks upwards into the uterus. The loop and string at bottom are used to remove the IUD if it is no longer needed.