Merck Manual

Please confirm that you are not located inside the Russian Federation

honeypot link
Quick Facts

Intrauterine Devices

By

The Manual's Editorial Staff

Last full review/revision Jun 2021| Content last modified Jun 2021
Click here for the Professional Version
Get the full details
Topic Resources

What are intrauterine devices (IUDs)?

An intrauterine device (IUD) is a type of birth control. It is a small T-shaped plastic device that a doctor can place in your uterus to prevent pregnancy. Your uterus is the organ where babies live and grow before they’re born.

IUDs are put into your uterus through your vagina (the muscular tube that connects your uterus to the outside of your body, also called the birth canal). A plastic string is attached to the IUD. The string lets you make sure the IUD is still in place and helps your doctor remove it.

  • IUDs work very well to prevent pregnancy and last between 3 and 10 years

  • IUDs don't have body-wide effects

  • A doctor must put in and remove your IUD

  • You can get pregnant immediately after removing an IUD

  • An IUD may change how much you bleed or cramp during your period

  • If put in within 5 days of sex, a copper IUD works as emergency contraception

Understanding Intrauterine Devices

Intrauterine devices (IUDs) are inserted by a doctor into a woman’s uterus through the vagina. IUDs are made of molded plastic. Two types of IUDs release a progestin called levonorgestrel. The other type is T-shaped and has a copper wire wrapped around the base and on the arms of the T. A plastic string is attached to the IUD. The string enables a woman to make sure the device is still in place and a doctor to easily remove it.

Understanding Intrauterine Devices

How do IUDs prevent pregnancy?

IUDs prevent pregnancy by:

  • Killing sperm

  • Preventing sperm from getting to your egg

  • If an egg does get fertilized, the IUD may also keep the fertilized egg from attaching to your uterus

  • IUDs don't remove a fertilized egg that has already attached to your uterus

What types of IUDs can I use?

There are 2 kinds of IUDs:

  • IUDs with hormones

  • IUDs containing copper (copper wire is wrapped around the device) instead of hormones

IUD with hormones

  • Lasts 3 or 5 years, or until removed by a doctor

  • About 1 in 100 women get pregnant while using it

  • Releases a hormone called progestin

  • May cause you not to bleed or bleed only a little during your period

Copper IUD

  • Doesn't give off hormones

  • Can be used as emergency contraception after having unprotected sex

  • Lasts 10 years, or until removed by a doctor

  • About 2 in 100 women get pregnant while using it

  • Can cause more bleeding and cramps during your period

Who can use IUDs?

Most women can use IUDs, including teenagers and women who haven’t had children.

You shouldn't have an IUD put in if you have:

You shouldn't have an IUD put in if you're pregnant.

What are problems with IUDs?

Problems that may happen with an IUD include:

  • IUD coming out by itself during the first year (more likely in women who are young or haven’t had children)

  • IUD punching a hole in your uterus when it’s put in (rare)

  • Increased chance of infection in your pelvis in the first month you have an IUD

  • Increased bleeding and cramps during your period (copper IUD only)

What are benefits of IUDs?

  • Birth control that works very well to prevent pregnancy

  • Lower chance of getting cancer in your uterus

  • Lighter bleeding during your period (hormonal IUDs only)

Drugs Mentioned In This Article

Generic Name Select Brand Names
MIRENA, PLAN B
NOTE: This is the Consumer Version. DOCTORS: Click here for the Professional Version
Click here for the Professional Version
Others also read

Test your knowledge

Loss of Smell
Anosmia is the total loss of smell. Most people with anosmia can taste sweet, sour, salty, and bitter substances but cannot distinguish among specific flavors. This is because the sense of smell makes it possible to distinguish among flavors, not taste receptors as many people erroneously believe. Which of the following is NOT a common cause of anosmia?
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID

Also of Interest

Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
TOP