Contains the hormone progestogen, which thickens cervical mucus to prevent sperm reaching an egg, and thins the lining of the uterus to prevent a fertilised egg implanting.

In some cycles it stops ovulation.

• Over 99 % effective if taken according to instructions.
• Can be used by women who cannot use estrogen.
• Can be used by women who smoke and are over 35 yrs.
• You can use it if you are breastfeeding.

• Periods may stop, or be irregular, light, or more frequent.
• May be temporary side effects such as spotty skin, breast tenderness, weight change and headaches.
• May get ovarian cysts.
• 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.