- Contraceptive coils (IUDs)
- What are contraceptive coils?
- How effective are coils?
- Other actions
- How does a coil work?
- How is a coil inserted?
- What does insertion feel like?
- Good advice
- Can any woman use a coil?
- What are the drawbacks?
- Less common problems with an IUD and an IUS
- What if you get pregnant?
- Where can I get a coil fitted?
- How long will the coil last?
- Emergency post-coital contraception
- Warning – fertility
Contraceptive coils (IUDs)
Written by Dr David Delvin, GP and family planning specialist and Christine Webber, psychotherapist
What are contraceptive coils?
Contraceptive coils are also called intra-uterine devices (IUDs) or intra-uterine contraceptive devices (IUCDs). They are little devices made of metal (usually copper) and plastic, which are ‘fitted’ or inserted into your womb by a doctor to prevent you from getting pregnant.
They are known as ‘coils’ or ‘loops’ because some of the early models were coil-shaped or loop-shaped. But now most look like a matchstick with a bar across the top – like the letter ‘T’ – and are about one and a half inches (4cm) long. Your womb is about the size of your fist.
Holding a matchstick in your closed fist gives a good idea of the size of a coil lying within the womb.
Some of the latest coils slowly release hormones into the womb for anything up to five years. This type of device is called an intrauterine system (IUS), and is inserted in a similar way to a standard IUD but has additional effects, both beneficial and adverse. The hormone in the type of IUS used in the UK (brand name Mirena) is levonorgestrel, which is a progestogen (a synthetic version of the natural hormone progesterone).
How effective are coils?
IUDs are a highly effective form of contraception, although not as effective as the Pill (combined oral contraceptive). Generally, if 100 women use the IUD for a year about two of them will get pregnant. Mirena has a lower failure rate because levonorgestrel adds to the contraceptive effect.
If 100 women used the Mirena IUS, less than one of them would be expected to become pregnant every year.
This is about the same as the figure for the Pill – but of course the efficiency of the Pill is very dependent on whether you remember to take it.
Standard IUDs tend to make periods heavier, longer and more irregular. The hormone in the Mirena thins the lining of the womb so although you may get irregular bleeding during the first few months, you should find that subsequently your periods become much shorter and lighter.
In fact, your periods might stop altogether. In addition, the IUS tends to reduce period pain. The Mirena is therefore a useful form of contraception if you tend to suffer from heavy or prolonged blood loss, particularly if it leads to anaemia, or if you get painful periods. (However, Mirena can cause lower abdominal pain and backache.) Some doctors may prescribe a Mirena simply for heavy or severely painful periods.
How does a coil work?
The mode of action of IUDs is still not fully understood, but it is thought that a coil works partly by thickening the mucus round the neck of your womb (cervix), thus making it difficult for sperm to get through to fertilize an egg. In addition, it might interfere with the passage and implantation (settling into the womb) of an egg. The Mirena IUS works in additional ways because of the hormone it releases.
It makes the lining of your womb thinner so that not only does it bleed less, but it is less likely to ‘accept’ an egg.
Furthermore, the Mirena seems to prevent ovulation (egg release) in some women, some of the time.
How is a coil inserted?
The coil is inserted through the cervix, which is at the top of your vagina. Coils must be put in by a specially trained doctor (or, in some countries, a specially trained nurse). If you want to find out about doctors who are trained to insert coils, contact your local Family Planning Clinic.
Initially, the doctor examines your vagina and then inserts a speculum (an instrument that holds the vagina open, allowing the doctor to see your cervix).
The doctor then slips an instrument shaped like a drinking straw through the small opening in your cervix, and up into your womb. This ‘straw’ contains the coil, and once it is in place the doctor pushes the device out of the tube and removes the tube. Coils are usually fitted during the last few days of a period, or just after.
Insertion usually takes about 10 minutes. Some women have a coil fitted immediately after a termination (abortion). After having a baby, a coil is usually put in about six weeks after childbirth. Occasionally, the doctor finds that she cannot manage to fit the coil and has to suggest other contraception.
What does insertion feel like?
Insertion can be slightly painful, although a few women find it very unpleasant. The amount of pain you feel generally depends on:
- how relaxed you are
- how skilled the doctor is
- the shape of your womb
- whether you have ever been pregnant – insertion is usually easy if you have had a baby.
Painkillers can be taken before the insertion if recommended by your doctor. Insertion of an IUS and larger IUDs can be more painful than smaller devices.
After a coil insertion:
- you should rest for at least half an hour.
- do not drive yourself home, just in case you feel faint.
- you may need aspirin or paracetamol for crampy pain over the next few hours.
- you may lose a little blood during the next few days.
- you can resume sex as soon as you like, and will be protected against pregnancy immediately – though not everybody feels like having sex the same evening!
Can any woman use a coil?
Coils are most suitable for women who have had children, but pose some risks for women with multiple sexual partners, because of the danger of infection.
A coil should NOT be inserted in:
- anyone who might be pregnant.
- anyone who has had an ectopic pregnancy (in which the foetus starts to develop in the wrong place).
- anyone who has had cancer of the ovary or the womb.
- anyone who has unexplained bleeding or pelvic pain.
- anyone who might have a pelvic infection or sexually transmitted disease.
- anyone who has major structural problems of the womb.
- anyone who has had surgery on their Fallopian tubes.
- (Mirena only) anyone who has had serious artery disease.
- (Mirena only) anyone who has an artificial heart valve.
A few women should NOT have IUDs that contain copper, including those who are allergic to copper and women with a liver condition called Wilson’s disease.
What are the drawbacks?
Coils can cause some problems.
Common problems with an IUD:
- Periods are usually heavier than before.
- Periods are usually longer than before.
- They can cause crampy pain during a period (although this tends to lessen over time).
- Initially, periods can be irregular.
- Later, periods are usually lighter, shorter, and may stop altogether (most women find this beneficial, but some would prefer to have a period).
Also, please note that coils can fall out. In some clinics, the expulsion rate is as high as 10 per cent.
It is a good idea to regularly check your vagina with your fingertips to ensure that the device is not coming down.
All you should be able to feel is the thread or threads (either one or two), which allow the doctor to pull the coil out when you eventually want it removed.
Less common problems with an IUD and an IUS
Pelvic infection: the risk of pelvic infection (also called pelvic inflammatory disease) is increased when you have a coil, especially if you have more than one sexual partner. Chief symptoms are fever, pelvic pain, and discharge, commonly occurring soon after insertion. Always report any of these symptoms to your doctor.
Perforation: occasionally, a coil may perforate (go through) the womb, usually at insertion. This is rare if the doctor or nurse is properly trained. It is important to realise that perforation is a serious matter: if the coil works its way inside your abdomen it could cause you severe pain and an operation might be needed to remove it. Always report any pain after coil insertion to your doctor.
The IUS has additional drawbacks due to the hormones it contains.
- Possible side effects of the hormone.
These include spots (maybe even acne), breast tenderness, headaches and weight gain.
- Ovarian cysts.
These fluid-filled swellings in the ovary occur in many women, and have no connection with polycystic ovary syndrome. In women with an IUS, they are probably due to the hormone. They may cause you some pain in the lower part of your tummy. They often go away of their own accord, and apart from pain, they are unlikely to produce symptoms, so they might not need any treatment. Always report any pain to the doctor.
- Possible unknown long-term effects.
Currently, the effects of the hormone in the Mirena (levonorgesterel) are claimed to be beneficial – particularly on menstruation. However, at the time of writing (October 2000), the device has been in widespread use only for a short period of time. So, any serious untoward long-term effects of the hormone might not be known for some years yet.
What if you get pregnant?
About 2 in 100 women who use an IUD for a year will get pregnant. Such a pregnancy carries a risk of being ectopic – meaning that the foetus starts to develop outside the womb, usually in one of the Fallopian tubes that conduct the egg from the ovaries to the womb. In this case, the foetus will nearly always die.
There will be pain and bleeding that might be severe and can be dangerous. The Mirena is claimed at the moment to have a low risk of ectopic pregnancy – about 0.06 per 100 women per year. Always report any unexplained pain or unusual or unexpected bleeding to a doctor.
Where can I get a coil fitted?
In the UK, most coils are fitted at Family Planning Clinics, though some are inserted by gynaecologists, or specially trained GPs. In other countries, the situation varies, but nurses working at special contraceptive clinics put in many coils.
The IUS must ONLY by put in by doctors who have specific training in its insertion.
How long will the coil last?
Some of the original IUDs were designed to last ‘forever’. But today’s devices generally work for between 3 and 10 years, depending on the brand. For instance, in the UK and Ireland at the moment, the following brands are available:
- Flexi-T 300 – lasts five years.
- GyneFix – lasts five years.
- Multiload Cu 375 – lasts five years.
- Multiload Cu 250 and Cu 250 Short – last 3 years.
- Nova-T380 – lasts 5 years.
- Mirena IUS – lasts 5 years.
Some women may have had a brand called Nova-T fitted. This lasts for five years but is no longer manufactured.
Emergency post-coital contraception
Mirena cannot be used for this post-coital contraception. Only standard IUDs are suitable. After unprotected sex (including after a condom has burst), an IUD can be inserted as a form of emergency contraception, as late as five days after the unprotected episode of sex.
But, the sooner a coil is put in, the better the protection. The success rate is variable, and is definitely NOT 100 per cent. In the UK at the moment, very few doctors are providing this method. Most post-coital IUDs are provided by Family Planning Clinics – but many of these clinics are closed through much of the week, and you may have trouble getting an urgent appointment.
Warning – fertility
In 2001, new research has been published that suggests that women who used IUDs in the past might have increased difficulty in getting pregnant.
Before having an IUD fitted, discuss this with the doctor.