At Somerset Early Scans we often see women who come to us for a pelvic scan to assess the location/position of their coil for “lost threads”. This is a brief guide to the IUS, and the pros and cons of using the hormonal coil for contraception or to treat menstrual problems.
What is an Intrauterine System?
The intrauterine system (IUS) is an effective method of contraception, and increasingly used to treat heavy, painful periods. The IUS sits inside the uterus. Once fitted, it works as a contraceptive for up to between three or five years, when it needs to be replaced. Most women who use an IUS will have no problems, but occasionally it’s use can lead to complications which are outlined below.
The IUS is a small, flexible, plastic device which sits inside the womb (uterus). There are two threads attached to it which pass out through the cervix and lie in your vagina. These allow you, and your doctor or practice nurse to check it is still there during a routine check-up. The threads or coil strings mean it can be removed easily. They do not hang outside the body and your partner shouldn’t be able to feel them during sex.
The IUS looks in shape like an Intrauterine Contraceptive Device (IUCD) – also known as the “copper coil”. However, the IUS does not contain copper; it contains slow-release progestogen hormone called levonorgestrel. It is therefore called an intrauterine ‘system’ (IUS) and not an IUCD.
Types of IUS
There are several types of IUS available. The different types of IUS vary according to their size and how much hormone they contain. The most commonly prescribed IUS in the UK is Mirena® and was the first IUS. It is also the largest and contains 52 mg levonorgestrel, and works for 5 years. The Jaydess® is smaller and contains a lower dose of levonorgestrel (13.5mg). It may be more comfortable to fit due to it’s smaller size.
How does it work?
They are all T-shaped (the two arms fold flat for insertion and then fold up for removal) and measure about the length of a matchstick. The length of the uterine cavity in which it fits is only a little longer, so the IUS fits snugly inside, and is always inserted by a trained doctor or nurse. Occasionally the IUS would be fitted by a gynaecologist in the hospital if the procedure is difficult.
The IUS works differently to an IUCD because it contains progestogen. The hormone thickens the mucus in the cervix, creating a plug which stops sperm getting through to the uterus to fertilise an egg. The hormone also makes the endometrium (lining of your womb) much thinner. This makes it unlikely that if an egg is fertilised, it will be able to implant there. An IUS also makes your periods much lighter, or they may disappear altogether. In some women it prevents ovulation, so that it happens less often or not at all. Once an IUS is inserted you no longer need to use other contraception for between three and five years. So, unlike women who take the contraceptive pill or mini pill, you don’t have to think about contraception every day. It is more than 99% effective when inserted correctly, and once in place, you don’t have to think about it. Although it contains progestogen, the quantity of the hormone which gets into your general system is very low. It does not usually therefore cause the side-effects which can occur with higher doses of hormones such as the implant.
Periods usually become lighter, less painful and often stop, unlike with the copper IUD. After 12 months most users only have a light bleed for one day per month or so, and about 1 in 5 users of the Mirena® IUS have no bleeding at all. For this reason, an IUS is sometimes recommended to treat heavy, painful periods and endometriosis.
An ultrasound scan is normally required prior to having an IUS fitted if you are experiencing heavy periods (menorrhagia), painful periods (dysmenorrhoea) or bleeding in between periods (intermenstrual bleeding). This is to exclude common conditions such as large fibroids or endometrial polyps which would prevent easy insertion of the IUS.
Although most women have no problems when they have an IUS, it can cause the following:
- Infection
There is a very small chance of infection during the first 20 days after an IUS is inserted. It is advisable to have a check for an existing infection before having an IUS fitted. Bacteria that cause Pelvic Inflammatory Disease (PID) can get into your body when an IUS is inserted.
- Irregular bleeding
You may have irregular bleeding for the first three to six months. This usually settles down and is usually just light “spotting” of blood.
Heavier bleeding can occasionally occur. If you experience heavy bleeding or a marked change in bleeding pattern you should discuss this with your doctor. It may mean the IUS has come out without you realising or could be a sign of infection or pregnancy.
- Lost Threads
You should tell your doctor or practice nurse if you can no longer feel the threads of your IUS. This can mean that the IUS has either been expelled from the uterus without you realising, or that perforation might have occurred. However, far more commonly it means that the threads are tucked up inside the cervix. Rarely, it can be because the threads have come off the IUS. The doctor or practice nurse will use a special instrument to check to see if they can retrieve the coil threads.
They would then request a transvaginal ultrasound scan to assess the uterus to see if the IUS is in the correct location. If ultrasound does not find the IUS, a CT will be ordered.
- Expulsion
The IUS may come out without you noticing. This happens to 1 woman in every 20. It usually happens in the first year, particularly in the first three months, during your period. Research has shown that it may be more likely to happen if it has happened to you before.
It is a good idea to check you can feel the threads of the IUS after your period. If you cannot feel them, you should use extra precautions such as a condom, until your doctor or nurse has checked the IUS is still there.
If the IUS has come out in the previous few days, you may need emergency contraception. If the IUS could have come out more than a few days previously, and you are sexually active, the doctor or nurse will need to make sure you are not already pregnant before fitting another one or starting alternative contraception.
- Perforation
The fitting of an intrauterine contraceptive can (very rarely) make a small hole in the uterus – this is called perforation. It protrudes through the wall of the uterus and may move into the pelvic or abdominal cavity. This happens in fewer than 2 women per 1,000, usually at the time of fitting. It can cause pain, but this is not usually severe and often there is no pain. The main symptom is not being able to feel the threads. Your womb will heal on its own, but you may need an operation to remove the IUS.
- Hormonal side-effects
Hormonal side-effects are uncommon. The progestogen released by the IUS mainly remains in the uterus and very little escapes into the bloodstream. So hormone side-effects are less common than with the contraceptive pill, progesterone only pill or implant.
If side-effects do occur, they tend to develop in the first few months. They then tend to ease and then disappear. Examples of possible side-effects include mood swings, fluid retention, sore breasts and a slight increase in breast size, acne and reduced sex drive.
- Ectopic pregnancy
It is rare to get pregnant with an IUCD or IUS in place, but if you do then it is more likely to be an ectopic pregnancy. An ectopic pregnancy develops outside the uterus, usually in the Fallopian tube. However, if you do develop one-sided abdominal or pelvic pain with bleeding you should discuss this with a doctor and do a pregnancy test.
When should it be removed?
The doctor or nurse will usually want to check that there are no problems a few weeks after fitting your IUS. It is best done after your next period. After this, there is no need for any routine check until it is time to remove the IUS. It can be taken out at any time by a trained doctor or nurse, and it is possible to get pregnant straight after it is removed.
Most women have no problems, and the IUS can remain in place for between three and five years, depending on the device fitted. However, if you are 45 years or over at the time of fitting, it can safely be left in place (and will remain effective) until your menopause.
The most important thing to remember is that you should consult a doctor if any of the following occur:
Prolonged abdominal pain after an IUS is inserted.
Vaginal discharge with or without pain. This may indicate infection.
You can’t feel your threads and suspect that the IUS has come out or is coming out. If you cannot feel the threads or feel something that feels like the head of a match, then use other contraception such as condoms until you have been checked by a doctor or nurse. An ultrasound scan is required to locate the IUS if they cannot retrieve the threads.