What is it?
- Injection of the hormone progesterone - given every three months by a health care professional.
How does it work?
- Stops ovulation (eggs being released from the ovaries), thickens the mucus at the entrance to the womb preventing sperm getting through and thins the lining of your womb preventing implantation of a fertilised egg.
What’s great about it?
- Very effective: If this method is used correctly and consistently, only 1 in 500 (>99%) of women will fall pregnant. Otherwise, as many as 6 in 100 women may become pregnant.
- No need to take pills or use something every time you have sex.
- Contraception lasts for 13 weeks.
- Periods may stop or become less frequent: after 1 year 50% women have no periods and by two years most women will not have periods.
- May help women with period problems e.g pain or heavy bleeding.
- Not affected by other medications, vomiting or diarrhoea.
- Can be used in women who cannot tolerate or use oestrogen containing contraceptives (pills/patch/ring) e.g. overweight women.
What’s not so great about it?
- No protection against sexually transmitted infections (STIs) - condoms advised.
- Periods may be irregular, heavier or prolonged. However bleeding tends to become less frequent and lighter or stop altogether after 6-12 months.
- Needs a regular injection by appointment with a health care provider.
- Some women gain weight, particularly those aged under 18 years of age, or those who are overweight to start with.
- May cause bone thinning, however this resolves when you stop receiving injections and is not associated with broken bones.
- Periods and fertility may take up to one year to return after stopping the injection.
- Can cause side effects e.g. mood change, reduced sex drive, spotty skin, tiredness, headache. Unacceptable side effects will usually not resolve until the injection wears off (up to 13 weeks).