Intrauterine system (IUS)

What is it?¹

The IUS is a small 'T' shaped device made from plastic containing progestogen that is inserted into the womb. It has two soft threads at one end that hang through the opening at the entrance of your womb (cervix) into the top of your vagina. It is normally fitted during the first 5 days of your period. If fitted at any other time an additional method of protection must also be used for 7 days.

Once fitted the IUS should be checked by your health professional 6 weeks after insertion. If you have any problems you can go back any time

How does it work?²

The IUS works by:

• Thickening the mucus of the cervix to act as a barrier to sperm
• Stopping a fertilised ovum from settling by keeping the lining of the womb thin
• In some women it stops ovulation

How effective is it?¹

It is over 99% effective and can be left in place for 5 years.

What are the benefits?

• Doesn’t interfere with sex
• Works for up to 5 years
• Usually decreases your period pain and amount of bleeding
• Fertility returns quickly when removed
• It is easily removed

Are there side effects?²

• Breast tenderness, spots, headaches
• Small chance of infection for 20 days after insertion
• Irregular spotting may occur
• There is a risk that the IUS might go through (perforate) your womb or cervix when it is put in. This may cause pain, but often there are no symptoms. If this happens the IUD will have to be removed by surgery

You should not use the contraceptive injection if you are/have had any of the following:

• Cancer of the womb or ovary
• Have breast cancer or have had breast cancer in the last 5 years
• Have active liver or gall bladder disease
• Unexplained bleeding from the vagina
• An untreated sexually transmitted infection or pelvic infection
• Have had problems with your womb or cervix

What are the drawbacks?²

• It takes some months for it to establish control over your periods
• During those first few months, you’re likely to have irregular (but fairly slight) bleeding
• The IUS can be pushed out of your womb (expulsion) or it can move. This is why your health professional advises you to check your threads every month
• There is a risk that the IUS might move through (perforate) your womb or cervix when it is put in. This may cause pain, but often there are no symptoms. If this happens the IUS will have to be removed by surgery

What do I do if I want to become pregnant?²

A trained doctor or nurse can remove the IUS at any time. If you want to try for a baby it is advisable to start pre-pregnancy care such as taking folic acid and stopping smoking before it is removed.

1. NHS direct. Health encyclopedia – IUS

2. fpa. Sex/sexual health – contraception – the intrauterine system