How to choose the right contraception

What it is

The progestogen-only pill (POP) contains a single synthetic hormone, a progestogen, in a much lower dose than that contained in the combined pill.

How it works

The POP acts as a contraceptive by:

• thickening cervical mucus so that sperm cannot swim through as easily
  
• thinning the endometrial lining of the womb so that, if an egg is fertilised, it can't implant or develop
  
• decreasing motility of sperm and eggs within the Fallopian tubes.

The progestogen-only pill is usually started on the first day of menstrual bleeding. Contraceptive protection is then achieved within about four hours. It's taken consecutively, every day, without a tablet-free break (even during menstruation), and must be taken within three hours of its due time in order to be effective. The mini pill has a failure rate of less than 1%, when taken regularly, as prescribed. Most pregnancies are the result of forgetting one or more pills, or not taking the pills on time. User error increases the failure rate to an average of about 4%.

Pros

• An easily reversible form of contraception.
  
• Suitable for older women, especially smokers.
  
• Suitable for use during breastfeeding.
  
• May relieve menstrual symptoms.
  
• No increased risk of blood clots or high blood pressure.
  
• Most menstrual bleeds occurring whilst taking the mini pill are light and regular, every 28 days, although they can appear irregularly.

Cons

• Must be remembered on time every day.
  
• If you take a mini pill just three hours late (ie 27 hours since the last tablet), you should take extra precautions (eg use condoms) immediately, and use these for the next seven days. If you miss two or more mini pills, emergency contraception should be considered.
  
• The mini pill seems to be less effective in women who weigh more than 70kg (11 stones).
  
• Vomiting or diarrhoea will interfere with absorption, and additional contraception should be used during the illness, and for one week afterwards.
  
• May dampen libido both while you take them and for some time afterward, according to recent studies
• Irregular periods can occur.
  
• There is a small increased risk of ectopic pregnancy.