An intra-uterine evice (intra meaning within, and uterine meaning of the uterus) is a birth control device placed in the uterus, also known as an IUD or a coil (this colloquialism is based on the coil-shaped design of early IUDs). Dr. Ernst Gräfenberg of Germany invented an early IUD and was the first person to market these devices. The IUD is the world's most widely used method of reversible birth control, currently used by nearly 160 million women (just over two-thirds of whom are in China where it is the most widely used birth control method, surpassing sterilization). The device has to be fitted inside or removed from the uterus by a doctor or qualified medical practitioner. It remains in place the entire time pregnancy is not desired. Depending on the type, a single IUD is approved for 5 to 10 years use (the copper T 380A is effective for at least 12 years).