IUS (Intrauterine system)

How effective is it?

Over 99 per cent effective.  Less than one woman in 100 will get pregnant over
five years.

How does it work?

A small T-shaped plastic device is put into the uterus.  It slowly releases the hormone progestogen.  
It thins the lining of the uterus to prevent a fertilized egg implanting.
It also thickens the cervical mucus.  This makes it difficult for sperm to meet an egg.

What are the advantages?

  • Works for five years but can be taken out sooner.

  • Periods usually become lighter, shorter and sometimes less painful or periods may stop altogether.

  • You do not have to think about contraception for as long as the IUS is in place.

  • When the IUS is removed your fertility will return to normal.

What are the disadvantages?

  • Irregular bleeding or spotting is common in the first six months.
  • Very small chance of getting an infection during the first 20 days after insertion.
May get ovarian cysts.
  • Insertion can be uncomfortable.

Anything else I should know?

  • If fitted after 45 it can stay in place until the menopause.

  • Women are taught to check the IUS is in place.

  • Can be useful for women with very heavy and/or painful periods.

  • A check for any existing infection is usually advised before an IUS is put in.

  • Not affected by other medicine.