Releases the hormone progestogen which stops ovulation, thickens cervical mucus to prevent sperm reaching an egg, and thins the lining of the uterus (womb) to prevent a fertilised egg implanting.
Advantages
Over 99% effective, lasts for 12 weeks (Depo-Provera) or eight weeks (Noristerat).
You can use it if you are breastfeeding.
You don’t have to think about contraception for as long as the injection lasts.
Not affected by other medicines, diarrhoea or vomiting.
Disadvantages
Periods may stop, be irregular or last longer.
Periods and fertility may take time to return after stopping the injection.
Some women gain weight.
The injection cannot be removed from the body so any side-effects may continue for as long as it works & for some time afterwards.
