The IUS (intrauterine system)

The IUS is a small plastic T-shaped frame that is inserted into the neck of the womb by a trained doctor or nurse. It contains a small amount of progestogen, the same hormone that's used in the mini-Pill. The hormone is released very gradually into the womb and it prevents pregnancy by thickening the mucus in the neck of the womb, making it difficult for sperm to enter. It also changes the lining of the womb so that it will not accept a fertilised egg. In some women it also prevents ovulation. Its effect is similar to the mini-Pill, but you don't have to remember to take a pill every day.

The IUS has 2 soft threads which lie inside the vagina so that you can check it's in place by giving it a gentle tug. It has to be replaced every 5 years by a trained health professional and can be removed at any time if you don't want to use it any more. After it's removed, you can get pregnant right away.

When you have an IUS fitted, your periods may be irregular with some bleeding in between periods for the first 3 months. After that your periods are usually lighter and shorter or you may have no bleeding at all.

How effective is the IUS compared to other methods?