The Contraceptive Implant

What is the contraceptive implant?

A contraceptive implant is a small tube that is put under the skin. It contains a progestogen hormone. Implanon is the only one prescribed in the UK at present. This is a tube 40mm long and 2mm wide (about the size of a hair grip).

The progestogen hormone in the implant is released slowly into the bloodstream at a steady rate. The progestogen works mainly by stopping ovulation (the release of the egg from the ovary). It also thickens the mucus made by the cervix which forms a 'mucus plug' in the cervix. This stops sperm getting through to the uterus (womb) to fertilise an egg. It also makes the lining of the uterus thinner. This means that if an egg was to fertilise, it is not likely to be able to attach to the uterus.

How effective is the contraceptive implant?

It is more than 99% effective. This means that less than 1 woman in 100 who uses this method of contraception will become pregnant each year. (Compare this to when no contraception is used. More than 80 in 100 sexually active women who do not use contraception become pregnant within one year.)

• You do not have to remember to take a pill every day.
• You only have to think about contraception every 3 years.
• It does not interfere with sex.
• It can be used when breastfeeding.
• Period pain is usually less than usual.
• It can used by some women who cannot take pills that contain oestrogen.
• It may help protect against pelvic infection. (The mucus plug in the cervix may help to prevent bacteria from travelling into the uterus.)

The release of progestogen will usually cause changes to the pattern of periods. During the first year it is common to have irregular bleeding. Sometimes periods are heavier and longer than before. They usually settle back into a regular pattern after the first year, but may remain irregular. In some women the periods become infrequent and light, or even stop altogether.

Some women worry about irregular or changed periods, but it does not mean anything is wrong and is of no consequence. However, unpredictable or irregular periods can be a nuisance.

Your doctor or family planning nurse will discuss any current and past illnesses. Some illnesses may mean you cannot use progestogen based contraceptives such as Implanon. However, the number of women this affects is small.

As with all hormonal contraceptives, some women report side-effects such as mood changes, breast discomfort, fluid retention, weight gain, headaches, and increase in acne. However, these are uncommon. If they do occur they tend to develop in the first few months only. They often go after 3-6 months if the implant remains. As with all small cuts to the skin there is a slight risk of a wound infection. The possible effects on periods are mentioned above.

• It is put in the inner side of the upper arm.
• It is usually first inserted within 5 days of a period starting. (This ensures that you are not pregnant.) It is effective from then on.
• An injection of local anaesthetic is used to numb the skin. A small cut is made and the implant placed under the skin. The wound is dressed and will soon heal just like any other small cut.
• The area around the implant may be bruised and sore for a few days, but this soon goes.

When is the implant taken out?

A replacement is needed every 3 years if you wish to continue with this form of contraception. It requires a small operation under local anaesthetic to remove it and put in a new one.

The implant can be taken out at any time if you request. It loses its effect immediately after being removed. So, if required, use other forms of contraception afterwards and for 7 days before it is removed. This is because sperm can survive for up to 7 days after sex.

Do other medicines interfere with the contraceptive implant?

Some prescribed medicines may interfere with the progestogen (mainly some used for epilepsy and TB). Tell the doctor or pharmacist that you have a progestogen implant if you are prescribed another medicine. It is unlikely that a medicine bought without the need of a prescription will interfere. If in doubt, ask the pharmacist.

Further information

Your GP, practice nurse, and pharmacist are good sources of information if you have any queries.
The fpa (formerly the family planning association) also provide information and advice.
fpa's Helpline: 0845 310 1334 or visit their website www.fpa.org.uk

Further reading

Contraception: a User's Handbook Anne Szarewski and John Guillebaud
Oxford Paperbacks 1998 2nd Ed ISBN: 0192861956

© EMIS and PIP 2004   Updated: August 2002   CHIQ Accredited