How does DMPA work?
DMPA works by:
- Preventing ovulation (egg release from the ovary)
- Thickening of the mucus of the cervix so that sperm cannot enter the uterus (womb)
How effective is DMPA?
DMPA is between 99% (only if the injection is not late and there are no other reasons why the medication would be less effective) and 94% effective. This means that of 100 women using DMPA consistently over a year, it is possible that 1 to 6 woman may become pregnant. The 99% is only true if you are not late with the injection.
What are the advantages of DMPA as a method of contraception?
- Long acting, effective method of contraception
- Inexpensive
- Undetectable by other people
- Suitable for women who can’t take contraceptives that contain oestrogen
Who can use DMPA?
Most women are suitable, though it is best used by women between 18 and 50 years of age. It can be used while breast feeding – a small amount of hormone gets into the milk but does not alter the quality of the milk.
Who should not use DMPA injection?
- Women with unusual bleeding that has not been investigated
- Women who may be pregnant
- Women with a current or past breast cancer or severe liver disease
- Women with a previous history of stroke or significant coronary heart disease
What are the disadvantages of DMPA as a method of contraception?
- DMPA changes bleeding/period patterns. These changes are a result of the hormonal effect to the lining of the uterus. It is not possible to predict which changes will occur, but they can include:
- During the first months of use, episodes of irregular bleeding and spotting lasting seven days or longer are common. The frequency and duration of such bleeding decrease with increasing duration of use.
- After one year of use, 50 percent of women have no periods and with ongoing use, this rate of amenorrhea (no periods) increases to 70 percent.
- Or irregular bleeding or spotting
- Sometimes, prolonged bleeding (this is usually light, but can be inconvenient for some women)
Heavy bleeding (rare)
- Fertility - possible delay in return to fertility; on average, the delay is about 9 months from the last DMPA injection.
- Return of fertility may be delayed after discontinuing DMPA. the average time to return to a previous menstrual pattern is 8 months after last DMPA. Within 12 months 78 percent of women who are trying to conceive will become pregnant. In a small proportion of women, fertility is not reestablished until 18 months after the last injection.
Other benefits of DMPA
- Women with heavier periods are likely to have no periods or lighter bleeding
- Women with period pain will have less or no pain - useful for endometriosis or premenstrual syndrome (PMS)
- Reduces the chance of anaemia caused by heavy periods
- Reduces the risk of cancer of the uterus
What are the possible side effects of DMPA?
DMPA has few side effects. However, side effects may include:
- Small weight gain in some women
- Headaches
- Acne
- Change in sexual interest
- Mood changes
The injection is long acting and if side effects occur they may last up to 3 months (it is not possible to reverse the effects of an injection once it is given).
Some side effects (especially bleeding changes) may persist beyond 3 months although there are a number of treatment options available with varying success that may help reduce bleeding problems if they occur.
What are the possible risks associated with DMPA?
DMPA use is associated with a slight loss of bone density while using the method. Continuing research studies currently suggest:
- This loss is largely reversible once DMPA use finishes
- Diet and exercise are other important influences on bone mass in young women
- There is limited evidence of an increase in fracture risk in women who use DMPA
How to start using DMPA
Starting DMPA for the first time requires an assessment by a doctor and a prescription.
This assessment enables you to ask any questions you may have and to be certain that it is the most suitable method for you.
The first injection of DMPA is usually given during the first five days of a period. In some cases condoms will need to be used for seven days after the first injection. It is very important that there is no chance of an early pregnancy at the time of injection as this may lead to a delay in the diagnosis of a pregnancy.
What do I need to know about the ongoing use of DMPA?
Follow up DMPA injections are given every 12 weeks to continue protection against pregnancy.
If you go beyond 12 weeks from your last injection you may be at risk of pregnancy.
If you aren't certain what to do, seek further advice as soon as possible, particularly if you think you may need Emergency Contraception.
To renew your DMPA prescription you will need to see a doctor for review once a year. A review of risks for loss of bone density (osteoporosis) will take place at this visit.