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Contraception health centre

IUD and IUS: Intrauterine device and intrauterine system

What are IUDs and IUSs?

IUDs and IUSs are ways to prevent pregnancy. They are types of long-acting reversible contraceptive (LARC) methods.

Although the Pill is the most common form of contraception the National Institute for Health and Care Excellence (NICE) says interest in LARC is increasing. Around 37% of women making contact with sexual health services in England in 2014-2015 did so for LARC.

An IUD, also known as the coil or intrauterine device, is a small, plastic and copper, flexible, T-shaped device that is placed into the uterus (womb) for contraception. There are various sizes and types of IUD available to suit the needs of different women. They can remain in the uterus for up to 10 years, depending on the type.

An IUS, or intrauterine system, is a small, T-shaped plastic device that contains progestogen. In the UK there are two of these available - Mirena can remain in the uterus for up to five years, and Jaydess can remain for up to 3 years.

How do they work?

IUDs contain copper which is slowly released into the uterine cavity. Copper stops sperm from reaching the egg and fertilising it.

The IUS releases the hormone progestogen, which causes the cervical mucus to become thicker so the sperm is less likely to reach the egg. The lining of the uterus is also altered, making implantation of a fertilised egg less likely.

How effective are the IUD and IUS?

IUDs and IUSs are over 99% effective.

How is an IUD or IUS used?

Once the IUD or IUS has been inserted by your doctor, you do not need to take any further steps to prevent pregnancy until it needs to be replaced. This will depend on the type of device used.

Are there side effects associated with IUDs and IUSs?

IUDs and IUSs rarely cause serious side effects, but when they do occur they include painful and heavy periods and backache. Before going ahead with this method of contraception, talk to the doctor, nurse or family planning expert about side effects and whether the device is suitable for you.

Do IUDs protect against sexually transmitted infections?

No. IUDs do not protect against sexually transmitted infections (STIs). The best safer sex method is the male condom.

Can the coil be used as emergency contraception?

Yes. NICE says the IUD or coil is the most effective method of emergency contraception.

It is effective at preventing pregnancy for up to 5 days after unprotected sex, or within 5 days of expected ovulation.

WebMD Medical Reference

Medically Reviewed by Dr Rob Hicks on September 08, 2016

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