How to choose the right contraception

What it is

The intra-uterine system (IUS) is a hormonal method of contraception, which delivers a progestogen hormone (levonorgestrel) directly into the uterus via an intra-uterine contraceptive device.

How it works

The IUS acts as a contraceptive by:

• changing cervical mucus so that sperm swim through less easily
  
• slowing movement of sperm through the uterus and the Fallopian tubes
  
• suppressing the normal 'plumping up' of the womb lining, so that a pregnancy is less likely to develop
  
• interfering with the development of ovarian follicles (although it does not completely suppress ovulation).

The IUS is as effective as female sterilisation, with less than two out of every 1,000 women using the method becoming pregnant per year, but it is also readily reversible.

Pros

• Remains effective for up to five years before needing to be replaced.
  
• As only a small amount of levonorgestrel is delivered, blood levels remain low - equivalent to taking just one to two progestogen-only mini pills per week - so there is minimal risk of side-effects.
  
• Unlike other IUCDs, it doesn't increase the risk of pelvic inflammatory disease, and may even protect against it.
  
• Periods become much lighter and, for one in five women, have stopped altogether within a year.
  
• Excellent treatment for heavy bleeding - can be used as an alternative to hysterectomy in some cases.

Cons

• Must be inserted by a trained healthcare professional.
  
• Insertion can be uncomfortable.
  
• Irregular bleeding and spotting can occur, especially during the first three months of use.
  
• Occasional side-effects at the start of treatment include headache, breast tenderness, skin problems and nausea.