IUS: How does it work and what are the pros and cons for patients?


An IUS is a small, T-shaped plastic device inserted into a patient’s uterus for the purposes of preventing pregnancy. Although it has a lot of similarities to the intrauterine device (IUD), it releases the hormone progestogen into the uterus instead of copper.

How it works

The IUS device works by thickening the cervical mucus, reducing the ability of sperm to reach the cervix. It also thins the lining of the uterus, so that if an ovum was to be fertilised it would be very hard to implant itself.

Most people continue to ovulate when using an IUS, both some don’t.

Advantages of the IUS

The IUS is a popular method of contraception in the UK. Advantages include:

    • It’s over 99% effective when inserted properly
  • Depending on the brand, it offers between 3 and 5 years’ contraceptive protection
  • Periods can become shorter, lighter and less painful. Many women report their periods stopping altogether after they’ve used the device for a year
  • The IUS is safe for breastfeeding mothers
  • It doesn’t interrupt sex
  • There’s no evidence that an IUS will increase the risk of cervical cancer, womb (uterus) cancer or ovarian cancer
  • Pregnancy can occur as soon as the device is removed
  • It’s a good option for those who can’t take the hormone oestrogen – the active ingredient in the combined contraceptive pill
  • It’s not affected by other medicines


The IUS certainly has many advantages but it is also vital to discuss the downsides with your patient too. For example:

  • Periods may stop altogether which some women may not feel comfortable with. Periods might also become very irregular
  • Some people experience mood swings, or other side effects like breast tenderness, acne and headaches. However these should be temporary.
  • Fluid filled (benign) cysts on one or both ovaries have also been connected with IUS use. No treatment is usually required though.
  • Although the IUS helps prevent pregnancy it doesn’t offer protection against STIs
  • Some patients may experience pelvic infections due to their IUS
  • Vaginal pain and bleeding are also (uncommon) side effects for some people

Concerning signs to watch out for

If your patient has an IUS fitted and they are displaying any of the following symptoms then urgent examination should be carried out. They include:

  • Swelling, tenderness or pain in the lower abdomen
  • Abnormal or smelly discharge
  • A high temperature
  • Fever symptoms, such as chills, a severe headache, body aches or hallucinations

There’s also a small chance that the IUS can be rejected (expelled) by the uterus or it can become displaced.

Patients who can’t feel the threads of their IUS or who are experiencing unusual bleeding will also need to be closely monitored.

Get to grips with all things contraception and sexual health

If you’re a healthcare professional who regularly gives advice to patients about their contraceptive options, you may well find our Contraception and sexual health workshop for the primary care practitioner course useful.

Devised specifically for nurses, health visitors, youth workers and other front line health professionals, we’ll look at the different types of contraception alongside their risks and benefits.

Worth 14 hours of CPD, the course takes place over 2 days. Held via Zoom it’s the ideal way to network and learn online in a convenient, safe way. 

All course materials and a certificate will be provided so why not take a look today and secure your place.