What is a Mirena coil?

What is a Mirena coil?
A Mirena coil, also called a hormonal coil, is an intrauterine birth control system (IUS) that is over 99% effective in preventing pregnancy. Mirena coils are recommended for women who have already had one child although they can be inserted in those that have never had a child. They are small, T-shaped plastic IUS devices that a healthcare provider places directly into the endometrial cavity of the uterus.
Mirena coils provide long-term birth control that is minimally invasive and very effective. They can also be used to treat a variety of conditions, including heavy periods, endometriosis, chronic pelvic pain, adenomyosis and anaemia. Mirena coils provide a number of advantages over other forms of birth control. They can be used while breast-feeding and users have the reassurance of effective birth control.
How does it work?
A Mirena coil works primarily by preventing fertilization of the egg, and to a lesser degree also inhibits implantation of the egg into the lining of the uterus. Mirena coils release a type of progesterone called levonorgestrel at a constant daily rate. The higher level of progesterone causes the user’s cervical mucus to thicken hindering the survival of sperm and inhibiting their ability to penetrate the egg. Additionally, the growth of endometrial tissue (the uterine lining) is suppressed, which prevents an egg from implanting into the wall of the uterus. In some users, ovulation is also prevented.
How long does it last?
Mirena coils are effective for up to five years after they are initially inserted, and have also been found to be effective for as long as seven years.
Is it reversible?
Yes – hormonal Intrauterine Systems like the Mirena coil are designed to be long-acting and completely reversible. That means that you can have your health care provider remove the Mirena coil at any time and resume normal sexual activity when wanting to start a family.
How do you know it will stay in place?
An Intrauterine System like the Mirena coil is specifically designed to stay in place until your healthcare provider removes it. If the Mirena coil does accidentally slip out of place – something that happens very rarely – it will most likely happen in the first few months of using it or while you are having your period when it is most important for you to check for your IUS strings to make sure it’s in place. Schedule a check up with your healthcare provider within three months of having it inserted, or after your first period following insertion.
What happens when the strings cannot be seen or felt?
If you check for your Mirena coil strings and can’t see or feel them, don’t worry. This might be an indication that the coil has slipped out of place, but it can happen for other reasons as well even when the coil is in place. This is most likely to occur during your period, so you should check your sanitary pad or tampon to make sure the coil hasn’t slipped out. If you can’t see or feel the strings, or if you think it may have moved out of position or fallen out, contact your healthcare provider to schedule a check-up. It’s a good idea to schedule periodic IUS check up at the same time as your gynaecological check-up.
What role does ultrasound play in determining position?
Typically, you and /or your healthcare provider can check the position of the coil even when the strings cannot be seen or felt using a thread collector device or a simple forceps. If your healthcare provider cannot locate the strings even with this method your Mirena coil may be out of position. When this happens they may decide to schedule you for an ultrasound scan to check the position of the coil. Ultrasound can determine whether the coil has moved out of position or has been expelled without you noticing. It is common to find the Mirena in its expected position even when the strings cannot be felt.
Is ultrasound a reliable way to determine position?
Numerous studies have shown that ultrasound is a reliable way to demonstrate the position of the Mirena coil. Ultrasound can quickly and dependably determine whether the coil has slipped out of position or is absent altogether.
Can you become pregnant with a Mirena coil?
While it’s very unlikely, there is a small chance that you could become pregnant even if you are using a Mirena coil. If the device is used properly, that risk is typically lower than 1.5%, according to the majority of studies into the effectiveness of plastic intrauterine birth control devices. If you do accidentally get pregnant while using a Mirena coil – which is highly unlikely – the coil can increase your chance of complications. If you are using a Mirena coil and suspect that you might be pregnant, schedule an appointment with your healthcare provider immediately.
Can you become pregnant easily when it is removed?
You can begin trying to conceive as soon as your Mirena coil is removed. The likelihood of conceiving after your Mirena coil is removed is about the same as the average young couple, or less than four to six months. One year after the coil is removed about 90% of couples trying to conceive will successfully do so.

Why use a Mirena coil or similar hormonal intrauterine device for contraception?
The main reason to use a Mirena coil for contraception over other birth control methods is the fact that it is highly effective and very convenient. Mirena coils are over 99% effective – making them the most reliable birth control device – and once it is in place, you do not have to do anything extra to ensure you are protected during intercourse.
Checking to make sure it is in place is very simple and when you decide that you do want to get pregnant, you can have your Mirena coil removed at any time and immediately begin trying to conceive. Mirena coils are oestrogen-free, which is another major advantage. They’re also approved to treat heavy periods and other medical conditions without relying on prescription drugs.

Sources:
http://www.nhs.uk/Conditions/contraception-guide/pages/ius-intrauterine-system.aspx
http://www.mirena-us.com/
http://www.jultrasoundmed.org/content/26/10/1389.full