What is the contraceptive injection?
The contraceptive injection or DMPA (Depot Medroxyprogesterone Acetate) is a long acting reversible contraceptive (LARC). It is a hormonal contraceptive containing a progestogen which is a type of hormone used in many contraceptives. DMPA has been available as a contraceptive method for many years.
How is it given and how often?
DMPA is given by injection in the arm or buttock by a doctor or nurse. It is given every 12 weeks.
How does it work?
The contraceptive injection works by preventing ovulation (stopping an egg being released from the ovary). It also thickens the mucus in the cervix which makes it difficult for sperm to enter the uterus (womb)
How effective is the contraceptive injection?
The contraceptive injection is a highly effective method of contraception, with a failure rate of less than 1% if it is given on time every 12 weeks.
What are the possible side effects?
The most common side effect of DMPA is a change in menstrual bleeding. Many women find their bleeding ceases altogether over time. This has no harmful effects and most women using DMPA find this a very positive side effect. Some women will continue to experience light irregular bleeding and a small number of women may experience heavy or longer bleeding.
Other possible side effects include:
A small weight gain in some women, headaches and mild acne. Although some women report a change in mood or sexual interest, the evidence for DMPA as a direct cause of this is not strong. Some women report positive or negative effects on mood or sexual interest, but most report no change.
What are the advantages?
- It is a highly effective contraceptive
- It is relatively inexpensive
- It only needs to be given every 12 weeks
- Commonly there is lighter or no bleeding
- It can reduce period pain, heavy periods and PMS for women who experience these
- It can reduce anaemia resulting from heavy periods
- It is suitable for women who cannot use oestrogen containing contraceptive
What are the disadvantages?
- There can be a delay to the return of normal fertility in women who use DMPA. On average this is around 8 months following the last injection. For this reason it is not recommended for use in women who are considering pregnancy in the near future. DMPA does not affect fertility in the long term.
- There is evidence that there is a small reduction in the density of the bones while women are using DMPA. This effect is reversed when it is ceased.
- Once the injection has been given the effect will be present for 3 months.
- You will need to see a health care professional every 12 weeks for the injection.
Who can use the contraceptive injection?
Most women can use the contraceptive injection. It is considered safe to use while breast feeding.
Who may not be suitable to use the contraceptive injection?
- Women who have a history of breast cancer
- Women with a history of stroke or heart disease, or who have risk factors for these conditions
- Women who have unexplained vaginal bleeding that might indicate a serious underlying condition
- Women with a history of severe liver disease or liver tumours
- Women who may be pregnant
- Women who are considering pregnancy in the near future
How do I start the contraceptive injection?
A doctor’s appointment is needed for assessment and for the prescription to be issued. This will also give you an opportunity to discuss this method of contraception and to ask any questions.
The first injection needs to be given within 5 days of the start of your period. This ensures that there is no risk of pregnancy at the time.