What is an Intrauterine System (IUS)?
Commonly known as Mirena in Australia, this is a small, plastic, T shaped device with a cylinder around its stem that releases the hormone levonorgestrel to prevent pregnancy. It is referred to as a ‘system’ to distinguish it from the copper-bearing IUDs which do not release hormones. As with the IUD, the IUS is placed inside the uterus by a doctor and can stay in place for up to 5 years. It can be easily removed by the nylon string which is attached to it. It is important to check the length of the string initially at 6 weeks then once a year, to make sure the device has not shifted and is correctly in place. The cylinder component of the IUS is covered with a membrane that regulates the release of the hormone levonorgestrel, which changes the lining of the uterus so that it does not get thick enough to allow the egg to grow in it, even if the egg is fertilised. The release of this hormone also causes the mucus in the cervix to become thicker so that sperm cannot enter the uterus. In
