IUS stands for Intrauterine System. It is also known as a Mirena® coil. It is similar to the IUD (or ‘coil’) in that it is inserted into the uterus to prevent pregnancy. However, unlike the IUD, it also contains a slow release hormone called Progestin which thins the lining of the uterus and thickens the mucus of the cervix to further decrease the risk of pregnancy (a Mirena® coil is over 99% effective if fitted properly). It is also a better option for women who suffer from heavy periods, as it can make them lighter or even stop them altogether. However it can have similar side effects to the contraceptive pill.