Progestogen-only pill (POP)

How effective is it?

Over 99 per cent effective if taken according to instructions.  Less than one woman in 100 will get pregnant in a year.

How does it work?

Contains the hormone progestogen, which thickens cervical mucus to prevent sperm reaching an egg.   In some cycles it stops ovulation.

What are the advantages?

  • Can be used by women who cannot use oestrogen.
  • Can be used by women who smoke and are over 35.
  • May make periods stop, become lighter or less frequent.

What are the disadvantages?

  • Periods can become irregular and sometimes more frequent.
  • May be temporary side-effects such as acne, weight change and headaches.
  • May get ovarian cysts.

Anything else I should know?

  • It needs to be taken at the same time each day.
  • Not effective if taken over three hours late (12 hours for Cerazette) or after vomiting or severe, long-lasting diarrhoea.
  • Some medicines may make it less effective.