Contraceptive implants and injections

Page last reviewed: 13/07/2011

Contraceptive implants and injections are long-acting, effective methods of contraception. They are over 99% reliable in preventing pregnancy, which means that less than one in 100 women who use the implant or injection will become pregnant each year.

The implant and the injections work in the same way: by slowly releasing a hormone called progestogen into your body. They do not protect you against sexually transmitted infections (STIs).

They can be started at any time during your menstrual cycle, as long as you and your doctor are reasonably sure that you are not pregnant.

Implants

There is currently one type of contraceptive implant used in Ireland called Implanon .

Implanon is a small (4cm), thin flexible tube. It is implanted under the skin of your upper arm by a doctor or nurse, using a local anaesthetic to numb the area. The small wound made in your arm is closed with a dressing and does not need stitches.

Implanon works for up to three years before it needs to be replaced. You can continue to use it until you reach the menopause.

The implant can be removed at any time by a specially trained doctor or nurse. It takes a few minutes to remove, using a local anaesthetic. 

As soon as the implant is removed, you will no longer be protected against pregnancy. If you want to use a different method of contraception after the implant, you will need to start this seven days before the implant is removed. This is because sperm can survive in the womb for up to seven days after sex.

Injections

The contraceptive injection is usually given into a muscle in your bottom, but sometimes into a muscle in your upper arm.

  • Depo-Provera is the most commonly used injection and is effective for up to 12 weeks, after which another injection is given.

Where to get them

You can get an injection or implant at your GP surgery or a genito-urinary (GUM), contraception or sexual health clinic. It will be given to you by a specially trained doctor or nurse.

Who can use them

Most women can be fitted with the contraceptive implant or given the contraceptive injection. They may not be suitable for you if you:

  • think you might already be pregnant,
  • want your periods to remain regular,
  • have bleeding in between periods or after sex,
  • have arterial disease or a history of heart disease or stroke,
  • have a blood clot in a blood vessel,
  • have liver disease,
  • have migraines, or
  • have (or have had) breast cancer.

Local anaesthetic

A local anaesthetic is a drug that is injected by needle or applied as a cream. It causes a loss of feeling in a specific area of the body.

Page last reviewed: 13/07/2011

Contraceptive implants and injections steadily release the hormone progestogen into your bloodstream.

Progestogen is very similar to the natural hormone progesterone, which is released by a woman's ovaries during part of the menstrual cycle.

The continuous release of progestogen:

  • stops you from releasing an egg every month (ovulation),
  • thickens the mucus from the cervix, making it difficult for sperm to pass through to the womb and reach an unfertilised egg, and
  • makes the lining of the womb thinner, so it is unable to support a fertilised egg.

Glossary

Uterus 
The uterus (or womb) is a hollow, pear-shaped organ in a woman where a baby grows during pregnancy.  
Ovaries
Ovaries are the pair of reproductive organs that produce eggs and sex hormones in women.

Page last reviewed: 13/07/2011

Contraceptive implant

The contraceptive implant Implanon can be fitted at any time during your menstrual cycle.

  • If it is fitted during the first five days of your cycle, you will be immediately protected against pregnancy.
  • If it is fitted on any other day of your cycle, you will not be protected for up to seven days. Use condoms or another method of contraception during this time.

You can have it fitted after you have given birth, usually after three weeks.

  • If it is fitted on or before day 21 after the birth, you will be immediately protected against pregnancy.
  • If it is fitted later than day 21, you will need to use extra contraception for the following seven days.

It is safe to breastfeed if you have had an implant fitted

The implant can be fitted immediately after a miscarriage or an abortion and you will be protected against pregnancy straight away.

Contraceptive injection

Contraceptive injections can be given at any time during your menstrual cycle:

  • If you have the injection during the first five days of your cycle, you will be immediately protected against pregnancy.
  • If you have the injection on any other day of your cycle, you will not be protected for up to seven days. Use condoms or another method of contraception during this time.

You can have injections after you have given birth, usually after six weeks when you are less likely to have heavy and irregular bleeding:

  • If you start injections before day 21 after the birth, you will be immediately protected against pregnancy.
  • If you start them later than day 21, you will need to use extra contraception for the following seven days.

It is safe to breastfeed after you have started your injections

Page last reviewed: 13/07/2011

The main advantage of contraceptive implants and injections is that they protect against pregnancy soon after the implant is put in or the first injection is given. Their effects are long lasting and your fertility returns when you stop using them.

Contraceptive implant

  • The implant works for about three years (it usually needs replacing every three years).
  • It does not interrupt sex.
  • It is an option if you cannot use oestrogen-based contraception.
  • You do not have to remember to take a pill every day.
  • It is safe to use if you are breastfeeding.
  • Your fertility should return to normal as soon as it is removed.
  • It offers some protection from pelvic inflammatory disease (the mucus from the cervix may stop bacteria entering the womb) and may also give some protection against cancer of the womb.
  • It may reduce heavy, painful periods after the first year of use.

After it has been inserted, you should be able to do normal activities (the implant will not break or move about).

Contraceptive injections

  • Each injection lasts for either eight or 12 weeks.
  • The injections do not interrupt sex.
  • They are an option if you cannot use oestrogen-based contraception.
  • You do not have to remember to take a pill every day.
  • They are safe to use if you are breastfeeding.
  • They are not affected by other medicines.
  • They may reduce heavy, painful periods and help with premenstrual symptoms for some women.
  • They offer some protection from pelvic inflammatory disease (the mucus from the cervix may stop bacteria entering the womb) and may also give some protection against cancer of the womb.

Page last reviewed: 13/07/2011

Contraceptive implant

Disrupted periods

Periods may change significantly in the first year of using Implanon. They will usually become irregular and may become very heavy, shorter and lighter, or stop altogether.

This may settle down after the first year, but occasionally continues as long as the implant is fitted.

Other side effects

Some women report the following:

  • headaches,
  • acne,
  • nausea, and
  • breast tenderness.

These usually stop after the first few months. If you have prolonged or severe headaches or other side effects, see your doctor.

Infection

In rare cases, the area of skin where the implant has been fitted can become infected. If this happens, the area will be cleaned and may be treated with antibiotics.

Contraceptive injections

It can take up to 12 weeks for injected progestogen to leave the body. If you have any side effects, they may continue during this time and for some time afterwards.

Disrupted menstrual cycle

Periods may change significantly in the first year of using contraceptive injections. They will usually become irregular and may be very heavy, shorter and lighter, or stop altogether. This may settle down after the first year, but occasionally continues as long as the injected progestogen remains in the body.

It can take a while for your periods and natural fertility to return after you stop using the injection. It takes around eight to 12 weeks for injected progestogen to leave the body, but you may have to wait longer for your menstrual cycle to return to normal if you are trying to get pregnant.

Until you are ovulating regularly each month, it can be hard to work out when you are most fertile for conception. In some cases, it can take three months to a year for your periods to return to normal.

Weight gain

You may put on weight when you use contraceptive injections, although some women lose weight. Use of the injections may be associated with an increase in weight of up to 2-3kg over one year.

Bone risk

Using contraceptive injections can cause thinning of the bones but does not increase your risk of bone fracture. Your bone replaces itself when you stop the injection, so it does not appear to cause any long-term problems.

Other side effects

Some women report the following:

  • headaches,
  • acne,
  • tender breasts, and
  • changes in mood and/or sex drive.

Breast cancer risk

Current research suggests that women who use hormonal contraception, such as the implant or injection, appear to have a slightly higher risk of being diagnosed with breast cancer compared with women who do not use hormonal contraception. Further research is ongoing.

Content provided by NHS Choices www.nhs.uk and adapted for Ireland by the Health A-Z.

Browse Health A-Z