by Samuel Zev Williams, M.D., Ph.D. Health Professional

What is an IUD?
An IUD is a type of contraceptive (birth control). IUD stands for Intrauterine Device. This form of birth control can also be called an IUC (intrauterine contraceptive). An IUD is a reversible form of birth control.

What does an IUD look like?
IUDs that are available in the United States are T-shaped. The stem is about 1 inch long and the arms are each about 0.5 inches long. A thin thread is attached to the bottom of the T.

What are they made of?
There are two types of IUDs available in the United States. In both types, the body of the IUD is made of plastic (polyethelene). One type of IUD has a copper band around the stem and arms. This is called a copper IUD. The other type of IUD has a hormone contained in its stem where it is slowly released. The hormone is called levonorgestrel and it is similar to progesterone. The same type of hormone is found in most birth control pills.

How do IUDs work?
Fertilization refers to the binding of a sperm and egg. This normally occurs in the fallopian tubes. The fallopian tubes run from the ovary to the uterus. Following fertilization, the fertilized egg begins to travel along the fallopian tube and into the uterus. As it travels, it undergoes several rounds of division. The growing mass of cells is called an embryo. The embryo then enters the uterus (womb) and implants into the wall of the uterus where it will grow until the time of delivery.

The exact mechanism of action of IUDs is not known. However, IUDs seem to prevent pregnancy from occurring by acting at several steps along the processes. For example, it appears that IUDs prevent sperm from reaching the egg. IUDs may also prevent the embryo from implanting. IUDs do not appear to disrupt a pregnancy after it is growing inside the uterus- that means they are not considered to be abortifactants.

Understanding the Risks of Contraception]** Why is there a thread attached to the IUD?**
The thread is helpful to help your doctor ensure that the IUD is in the correct position (as will be explained below) and to help remove the IUD when it is time to take it out.

How is an IUD inserted?
An IUD is inserted in a doctor's office. The woman lays on the examination table with her heels in foot-holders. A speculum is placed in the vagina to allow the doctor to visualize the cervix. A soap-like solution is then used to clean the outside of the cervix. Sometimes a clamp (tenaculum) is placed on the cervix to help the doctor hold the cervix and position the uterus. A thin piece of plastic or metal is then passed through the cervix and into the uterus. This allows your doctor to determine the path of your cervix and to measure the depth of your uterus. The doctor then uses this information to place a narrow tube containing the IUD into the correct position inside the uterus. The IUD rests inside this tube with the IUD arms folded. The IUD is then released from the tube into the uterus and the IUD arms extend open. The tube that carried the IUD is then removed leaving behind only the IUD and the tailing threads of the IUD that come out of the cervix. The threads are then cut so that about 1.5 inches of the threads are left outside of the cervix and within the vagina.

What happens next?
After the IUD is placed, your doctor may ask you to return to the office a week or two later for a "string check". A "string check" simply involves the doctor using a speculum to look at the cervix and make sure that the thread attached to the IUD is still seen and is about the same length and when it was inserted. This helps to confirm that the IUD is in the correct position and that it hasn't fallen out.

How is an IUD removed?
Removing an IUD is usually even easier then placing it. Removal of an IUD, like insertion of the IUD, occurs at your doctor's office. A speculum is placed just as it was during the IUD insertion. A clamp is placed on the IUD strings and the IUD is gently pulled out.

Is it painful to have and IUD placed or removed?
This varies from woman to woman. Some women experience only mild cramping or discomfort during insertion and removal of the IUDs whereas others can have more moderate pain.

How long can you keep your IUD?
The copper IUD can remain in-place and effective for up to 10 years. The hormone containing IUD can remain in-place and effective for up to 5 years. It is important to note that both IUDs can be removed prior to these dates. For examples, if a woman had a Copper IUD placed but 2 years later decided that she wanted to get pregnant, the IUD could be removed then.

What are the side effects of the IUD?
The most common side effect is mild cramping and discomfort that usually goes away within a few weeks. The copper IUD can cause periods to become heavier, but they generally remain regular. The hormonal IUD can cause periods to become lighter and some women stop getting a period altogether, but it can also cause spotting during the menstrual cycle.

Are IUDs safe?
In general, IUDs are very safe and very well tolerated. Within the first 3 weeks after the IUD is inserted there is an increased risk that if a woman gets an infection in the vagina or cervix, it can spread to the uterus and fallopian tubes and develop into pelvic inflammatory disease (PID). There is also a risk that when the IUD is being placed, it could be placed too deeply and push through the uterus and into the abdomen. When that occurs, a surgical procedure is required to remove the IUD. Thankfully, this is a rare occurrence- about 1 in every 1000 IUD insertions. Very rarely, a woman can become pregnant with an IUD in place. When this occurs there is a risk for an ectopic pregnancy (pregnancy outside the uterus such as in the fallopian tubes). So, if you have an IUD but think you might be pregnant, let your doctor know right away.

How effective is an IUD?
The IUD is highly effective and is considered one of the most effective methods of birth control. It is over 99% effective.

Do you have to have had children to have an IUD placed?
No. IUDs can be safely placed in women who have never had children or adolescents.

Who should not get an IUD?
IUDs should not be placed in anyone who may be pregnancy or who has an active pelvic infection such as with Chlamydia or gonorrhea. They should also not be placed in anyone with an abnormal uterus such as with severe fibroids because this makes it more likely for the IUD to fall out or for there to be difficulties in placing it. People with Wilsons disease (where there is too much copper in the blood) on an allergy to copper should not have the copper-IUD inserted. There are other contraindications, so be sure to speak with your doctor about any other medical problems.

For more information, be sure to check out:

Types of Emergency Contraception

What You Can Expect After Taking the Morning After Pill

Emergency Contraception: How Much Do You Know About the Morning After Pill?

The Morning After Pill

Samuel Zev Williams, M.D., Ph.D.
Meet Our Writer
Samuel Zev Williams, M.D., Ph.D.

Samuel Zev Williams is a nationally-recognized clinician and researcher in the area of recurrent pregnancy loss and infertility. He wrote for HealthCentral as a health professional for Sexual Health.