Contraception: injection

Choosing a method of contraception can be a difficult task for many individuals and couples in Australia. One method that is available is a hormonal contraceptive injection called depot medroxyprogesterone acetate (DMPA).

DMPA is a long-acting, synthetic version of the natural female hormone progesterone. Brands of DMPA that are available in Australia include Depo-Provera and Depo-Ralovera. DMPA injections provide reliable contraception for 3 months.

How does DMPA work?

Depot medroxyprogesterone acetate (DMPA) is a long-acting type of synthetic hormone (called a progestin) that mimics the action of the naturally-occurring hormone, progesterone. When given as a depot injection (which means the hormone is released slowly over several months), it provides reliable contraception for 3 months. If you need ongoing contraception, the injection should be repeated every 3 months.

The injection works in several ways. Firstly, DMPA stops ovulation (the release of an egg, or ovum, from the ovaries), which usually happens about once a month. With no egg released, pregnancy is impossible.

DMPA also changes cervical mucus (the natural discharge from the cervix), making it difficult for sperm to penetrate and enter the uterus (womb). DMPA also makes the lining of the uterus unfavourable for a pregnancy.

How effective are DMPA contraceptive injections?

Contraceptive injections are a very reliable method of contraception.

The effectiveness of all contraceptive methods can be measured for perfect use and typical use. With perfect use (when the contraception is used consistently and correctly), DMPA injections are extremely effective at preventing pregnancy. The reported failure rate of DMPA injections in the first year of perfect use is about 0.2 per cent (which is a failure rate of 2 in a thousand).

With typical use (what tends to happen in reality), contraceptive injections are slightly less reliable – the failure rate is around 6 per cent in the first year of typical use (6 failures for every 100 users). Typical use failures are generally due to running late with repeat injections. So to ensure that contraceptive injections are effective at preventing pregnancy, it’s important that you always remember to have your next injection on time – injections are needed once every 12 weeks.

Advantages of contraceptive injections

Some of the advantages of contraceptive injections with Depo-Provera or Depo-Ralovera include the following.

  • Contraceptive injections provide continuous contraception for 3 months. Once the injection has been given, nothing more needs to be done.
  • Contraceptive injections are very cost-effective.
  • This type of contraception is safe to use if you are breast feeding.
  • Depo-Provera and Depo-Ralovera are safe to use in women who cannot use forms of contraception that contain the hormone oestrogen.
  • Many women stop having periods and vaginal bleeding altogether with continued use of contraceptive injections. Symptoms associated with periods, including period pain, are also reduced. This can be especially helpful for women with endometriosis.

Disadvantages of contraceptive injections

Disadvantages of DMPA contraceptive injections may include the following.

  • Some women have unpredictable or prolonged vaginal bleeding when using DMPA. However, this usually settles within several months of use.
  • DMPA injections do not provide any protection against sexually-transmissible infections (STIs). An additional barrier method of contraception (such as condoms) should be used for protection from STIs.
  • After an injection, it is hard to predict when ovulation will restart. In some cases it can take as long as 18 months after stopping DMPA before fertility returns and pregnancy is possible. For this reason, Depo-Provera and Depo-Ralovera are not recommended for couples who are planning a pregnancy in the next year or 2.

How is DMPA used?

Visit your doctor or Family Planning Clinic if you are interested in long-term contraception. A doctor will ask some questions to determine whether depot medroxyprogesterone acetate (DMPA) is a suitable contraceptive option for you.

Your doctor will probably administer the injection of DMPA at a subsequent visit. They will recommend that you book your appointment at a suitable time in your menstrual cycle.

The best time in your cycle to receive the injection is during day 1 to 5 of your cycle, when you have your period. When you have the injection at this time, you are protected against pregnancy straight away. It is possible to have the injection at other times in your menstrual cycle, but you will need to use an alternative method of contraception, or not have sex, for at least 7 days after the injection.

Injections are usually given in the muscle of your buttocks or your upper arm.

Side effects of Depo-Provera and Depo-Ralovera

Your periods may be unpredictable and irregular when taking Depo-Provera and Depo-Ralovera. Some women have light vaginal bleeding or ‘spotting’, which is sometimes prolonged. In about 50 to 70 per cent of women using contraceptive injections for more than a year, periods and vaginal bleeding stop completely.

Other possible side effects include:

  • weight gain;
  • acne;
  • headaches; and
  • mood changes.

Long-term use may have an effect on bone density and this may need to be monitored. There may also be an increased risk of blood clots while using hormone injections for contraception.

DMPA is not suitable for some women, including those wishing to become pregnant in the near future, women over the age of 50 or women considered at risk of osteoporosis. Also, DMPA is not a suitable first choice for those younger than 18 years of age.

DMPA is also not recommended for women who have had breast cancer, stroke, ischaemic heart disease or liver problems.

Some women experience unpredictable or persistent vaginal bleeding for a while after stopping injections with medroxyprogestone acetate.

There are many ways of preventing pregnancy, each suiting some people more than others. Talk to your doctor if you think contraceptive injections may be the right choice for you.

Last Reviewed: 10 September 2016
myDr

Online doctor

Need health advice right now?See an Australian-registered doctor on your phone

References

1. Progestin-only contraception (published March 2014). In: eTG complete. Melbourne: Therapeutic Guidelines Limited; 2016 Mar. http://online.tg.org.au/complete/ (accessed Sep 2016).
2. Royal Australian and New Zealand College of Obstetricians and Gynaecologists. Depot medroxyprogesterone acetate (updated July 2015). http://www.ranzcog.edu.au/college-statements-guidelines.html (accessed Sep 2016).
3. Family Planning NSW. The contraceptive injection (updated May 2013). https://www.fpnsw.org.au/health-information/contraception/contraceptive-injection-dmpa-depo-provera%C2%AE-depo-ralovera%C2%AE (accessed Sep 2016).
myDr

myDr

myDr provides comprehensive Australian health and medical information, images and tools covering symptoms, diseases, tests, medicines and treatments, and nutrition and fitness.