The Coil: IUD and IUS

The coil is a small T-shaped plastic device that is inserted by trained professionals into your womb. It is one of the most commonly used contraception in the world, except in the UK where it is used less than the oral contraceptive pill.

There are 2 types of coil used: the IUD or copper coil and the IUS or Mirena coil.

How Effective is the Coil?

Both the IUD and IUS are over 99% effective if used correctly. This means that on 100 women following the methods for one year, only one of them would get pregnant.

How Does the Coil Work?

The IUD destroys sperm and, hence, stops them from reaching your egg. The IUS releases progesterone and therefore works in 2 ways: it causes the thickening of your cervical mucus so that sperm cannot get through; or it causes the lining of your womb to be thinner, so that there is less chance that a pregnancy could implant and progress.

The coils are both termed, long-acting, reversible contraception. The IUD can be used for 5 to 10 years and the IUS is used for 5 years.

A trained doctor in your local GP surgery or family planning clinic will be able to fit the coil. It usually takes approximately 20 minutes. The coil is effective immediately if inserted at the beginning of your period; otherwise it will take 7 days. All coils have threads that hang through your cervix that allow you and your doctor to check that the coil is in the correct position.

Advantages of the Coil as Contraception

You do not have to remember to take a pill each day. The coil does not interrupt sex, unlike condoms may be perceived as doing. If you have the IUS, your monthly period should become lighter and less painful. Some women do not have periods at all with the coil.

You can have the coil fitted 4 weeks after giving birth, even if you are breastfeeding. The IUD is useful if you cannot take hormonal contraception. The coils last for at least 5 years.

If you have the coil fitted after the age of 40 (IUD) or 45 (IUS), it can be left in until after you are menopausal.

Disadvantages and Risks

Some contraindications to having the coil include pregnancy, vaginal infections, abnormal womb anatomy, liver disease, breast or gynecological cancer, unexplained vaginal bleeding, or cardiovascular disease (e.g. heart attacks/strokes). The IUD can make your periods heavier and longer. You may also experience spotting and erratic vaginal bleeding. This tends to settle with time; however for some women, it becomes unacceptable and requires removal.

With the IUS, you might experience side effects of the progesterone itself, such as bloating, weight gain, headaches, breast tenderness, or mood changes

During insertion, there are small risks, including the coil making a hole in your womb (perforation), moving, or falling out (expulsion).

There is a small risk of womb infection in the first 3 weeks after insertion. Your GP may arrange for you to have vaginal swabs before inserting the coil to reduce this risk.

It may be difficult to remove the coil, especially if it has moved location and the threads cannot be seen. Your partner may also feel the strings from your coil; this means that you should return to your surgeon or family planning clinic for the threads to be shortened.

N.B. The coils don't provide any protection against sexually transmitted infections (STIs).

Further Sources of Information

You can find information about the IUD and on the IUS on the Family Planning Association website.

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