How effective is a contraceptive injection?
If used according according to the injection schedule it is over 99% effective. This means that less than 1 woman in 100 will get pregnant in a year.
How do contraceptive injections work?
The main way they work is to stop your ovaries releasing an egg each month (ovulation).
They also ;
- Thicken the mucus from your cervix. This makes it difficult for sperm to move through it and reach an egg.
- Make the lining of your womb thinner so it is less likely to accept a fertilised egg.
Can anyone use a contraceptive injection?
Most women who want to can have a contraceptive injection. Your history is the main guide to ascertain if you are suitable.for example, if you thought you were pregnant or did not want to change your periods it would not suit you.
It may also be unsuitable if have now or have had in the past
- breast cancer
- unexplained vaginal bleeding (for example, bleeding between periods or after sex)
- thrombosis (blood clots ) in any vein
- a heart attack or stroke
- high blood pressure
- diabetes with complications or diabetes for more than 20 years
- active liver disease
- risk factors for osteoporosis
What are the advantages of the contraceptive injection?
- you donít have to think about contraception for as long as the injection lasts.
- it doesnít interrupt sex
- you can use it if you are breastfeeding
- it is not affected by other medicines
Medical benefits would include
- it may reduce heavy periods and help with premenstrual symptoms for some women.
- it may give you some protection against cancer of the womb.
- it gives some protection against pelvic inflammatory disease.
- it is a good method if you cannot use estrogens (hormones), like those in the combined pill.
What are the disadvantages of the contraceptive injection?
- Your periods may change in a way that is not acceptable to you.
- Iirregular bleeding may continue for some months after you stop the injections.
- Women may put on weight when they use Depo-Provera but not all women put on weight and some women loose weight. Some women using Depo-provera for 1 to 2 years have reported putting on up to 8 pounds. Further wieght gain may occur if using Depo for a longer period of time.
- Other possible side effects include headaches, abdominal pain or discomfort, dizziness, spotty skin, tender breasts, bloating and changes in mood and sex drive. these will usually pass after a short while.
- The injection works for 12 weeks.
- A really important disadvantage is that it cannot be removed from your body so if you have any side effects, you have to be prepared for them to continue during this time and for some time afterwards.
- Your periods and fertility may take a few months to return after stopping Depo-Provera injections. Sometimes it can take more than a year for your periods and fertility to go back to normal.
- Contraceptive injections do not protect you against sexually transmitted infections, so you may have to use condoms as well.
Are there any risks?
- Using Depo-Provera may affect your bones.
- Research about the risk of breast cancer and hormonal contraception is complex and contradictory. Current research suggests that women who use hormonal contraception appear to have a small increase in risk of being diagnosed with breast cancer compared to women who donít use hormonal contraception. Further research is ongoing.
How does Depo-Provera affect my bones?
- Using Depo-Provera affects your natural estrogen levels, causing thinning of the bones. This is not normally a problem for most women as the bone replaces itself when you stop the injection and it does not appear to cause any long-term problems.
- Thinning of the bones may be more of a problem for women who already have risk factors for osteoporosis.
- It is also a concern for young women under 19 years old as the body is still making bone at this age. Although young women can use Depo-Provera, it is recommended that they should first consider all other suitable methods of contraception.
Will the injection affect my periods?
Your periods will probably change.
- In some women periods may stop altogether.
- Some women will have irregular periods or spotting, especially to begin with.
- Some women will have periods that last longer and are heavier.
These changes may be a nuisance but are not harmful. If you do have prolonged bleeding it may be possible for the doctor or nurse to give you some additional hormone (temporarally) or medicine that can help control the bleeding.
When can I start using a contraceptive injection?
You will usually be given an injection during the first 5 days of your period. You will immediately be protected against becoming pregnant. If you have the injection on any other day you will not be protected for the first 7 days, so you will need to use another method of contraception, such as condoms during this time.
When can I start the injection after having a baby, miscarriage or termination?
The injection is usually given from 6 weeks after you have given birth. or immediately after termination or miscarriage.
Can I use the injection if I am breastfeeding?
How is the injection given?
The hormone is injected into a muscle, usually in your bottom.
Can anything make the injection less effective?
While the injection is working there is nothing that will make it less effective.
Injectable contraception is not affected by:
- Prescribed medication including antibiotics.
- Any medicines which you buy over the counter at a pharmacy.
Can I use the injection if I am at risk of osteoporosis?
If you have risk factors for osteoporosis (thinning of the bone) it is normally advisable to use another method of contraception. The risk factors include:
- A lack of estrogen due to early menopause (before 35 years).
- A lack of estrogen due to missing periods for 6 months or more, as a result of over-exercising, extreme dieting or eating disorders.
- Heavy drinking.
- Long-term use of steroids.
- A close family history of osteoporosis.
- Certain medical conditions affecting the liver, thyroid and digestive system.
How long can I use the injection for?
You can continue to use Depo-Provera until the menopause, provided there are no medical reasons not to use it and you are not at risk of osteoporosis. If you do use the injection long term you should expect to have your risk factors for osteoporosis re-assessed every 2 years. A bone scan may be preferred.