To understand how the IUD works, you should know what happens during reproduction. A woman has two ovaries, one on each side of the uterus. Each month, one of the ovaries releases an egg into a fallopian tube. This is called ovulation. It typically occurs about 12-14 days before the start of the menstrual period.

A woman can get pregnant if she has sex around the time of ovulation. During sex, the man ejaculates sperm into the vagina. The sperm travel up through the cervix and into the fallopian tubes.

If a sperm meets an egg in the fallopian tube, fertilization--union of egg and sperm--can occur. The fertilized egg then moves down the fallopian tube to the uterus. It then attaches to the uterus and grows into a fetus.

Types of Intrauterine Devices

Although there have been several types of IUDs, currently only two are available in the United States: the hormonal (Mirena) and the copper. The hormonal IUD must be replaced every 5 years. It is FDA approved for both birth control and/or heavy/crampy menses.The copper IUD can remain in your body for as long as 10 years. As soon as the IUD is removed, there is no protection against pregnancy.

The IUD is more effective than most other forms of birth control. However, the IUD does not protect against sexually transmitted diseases (STDs).

The IUD is a very popular method of birth control throughout the world. However, in the United States, less than 1% of women using birth control use an IUD. Many women are afraid to use an IUD because one type had problems and was withdrawn from the market in 1975. Today's IUDs are safer and more effective. The design changed, and doctors are careful in selecting patients who can use them.

How an IUD Works

Both types of IUDs are T-shaped, but they work in different ways. The hormonal IUD (Mirena) releases a small amount of progestin into the uterus. This thickens the cervical mucus, which blocks the sperm from entering the cervix. It may make the sperm less mobile and make the sperm and the egg less likely to be able to live in the tube. It also thins the endometrium (lining of the uterus). This keeps a fertilized egg from attaching and makes menstrual periods lighter.

The copper IUD releases a small amount of copper into the uterus. A copper IUD does not affect ovulation or the menstrual cycle. It causes a reaction inside the uterus and fallopian tubes. This can prevent the egg from being fertilized or attaching to the wall of the uterus. The copper seems to work as a kind of spermicide. It prevents sperm from going through the uterus and into the tubes. It also reduces the sperm's ability to fertilize an egg.

Inserting the IUD

A doctor must insert and remove the IUD. Your doctor will perform a routine exam to make sure you're able to use one. It may include:

  • Reviewing your medical history
  • Performing a pregnancy test
  • Taking a sample from your vagina and cervix to check for infection

You may not be able to use an IUD if you have:

  • A uterine size or shape incompatible with the IUD
  • A recent abnormal Pap test result
  • Abnormal uterine bleeding

You may be asked to read and sign a consent form before using an IUD. Make sure you understand everything about the IUD to be inserted. If you have questions, ask your doctor.

The IUD is often inserted during or right after your menstrual period. The doctor puts the IUD in a long, slender, plastic tube. He or she places it into the vagina and guides it through the cervix into the uterus. The IUD is then pushed out of the plastic tube into the uterus. The IUD springs open into place, and the tube is withdrawn.

Insertion of the IUD does not require anesthesia (pain relief), although you may have some discomfort. Taking over-the-counter pain relief medication before the procedure may help. Sometimes a doctor will choose to use local anesthesia to insert the IUD.

You Should Not Use an IUD If You:

  • Are pregnant
  • Have a known or suspected pelvic cancer
  • Have undiagnosed vaginal bleeding
  • Have a known or suspected pelvic infection
  • Have multiple sex partners
  • Are at high risk for STDs
  • Have certain liver conditions (copper IUD only)

Once the IUD is inserted, the doctor will show you how to check that it is in place. Each IUD comes with a string or "tail" made of a thin plastic thread. After insertion, the tail is trimmed so that 1-2 inches hang out of the cervix inside your vagina. You will be able to tell the placement of the IUD by the location of this string. The string will not bother you, but your partner may feel it with his penis. This should not interfere with his sexual feeling.

It is important to check the string regularly. To do this, you must insert a finger into your vagina and feel around for the string. You can do this at any time, but doing it right after your menstrual period is easy to remember. If you don't feel the string or if you feel the IUD, call your doctor. The IUD may have slipped out of place. Use another form of birth control until your IUD is checked.

A doctor must remove the IUD. Do not try to remove it yourself.


During the first year of use, about 8 out of 1,000 women using the copper IUD will become pregnant. This makes it one of the most effective forms of birth control available. The hormonal IUD (Mirena) is even more effective. The IUD also has many other benefits:

  • It is easy to use. Once it is in place, you do not have to do anything else to prevent pregnancy.
  • It does not interfere with sex, daily activities, or menstruation. You can use a tampon with it.
  • Physical activity will not dislodge the IUD.


Serious complications from use of an IUD are rare. However, some women do have problems. These problems usually happen during, or soon after, insertion:

  • Expulsion: The IUD is pushed out of the uterus into the vagina. It happens within the first year of use in about 5% of users. This rate decreases with length of use. It is more likely to occur in women who have not had children. If the IUD is expelled, it is no longer effective.
  • Perforation: The IUD can perforate (or pierce) the wall of the uterus during insertion. This is very rare and occurs in only about 2 out of every 1,000 insertions. 
  • Infections: Infections in the uterus or fallopian tubes can occur. This may cause scarring in the reproductive organs, making it harder to become pregnant later. 
  •  Pregnancy: Rarely, pregnancy may occur while a woman is using an IUD. If the string is visible, sometimes the IUD can be removed. If the IUD is removed soon after conception, the risks caused by having the IUD in place are decreased. If the IUD remains in place, there can be risks to the mother and fetus, including miscarriage, infection, or preterm birth. However, pregnancy may go to term with an IUD in place. If you are using an IUD and think you may be pregnant, talk to your doctor about your options and risks.

Be alert for symptoms that may signal a problem with your IUD.

Side Effects

Menstrual pain and bleeding are increased with the copper IUD, but decreased with the hormonal IUD. Some women have some cramping and spotting during the first few weeks after the IUD is inserted. Vaginal discharge also can occur. These symptoms are common and should disappear within a month. Rarely, the hormonal IUD can lead to some acne, slightly increased hair growth, breast tenderness, and headaches.  Very few women have it removed due to these symptoms. The wonderful thing about the hormonal IUD is that there is a decreased amount of bleeding or no period at all!!  This is great for women who have had heavy periods or who are very active and desire less bleeding.  Occasionally spotting can occur unscheduled, but it will be very light. The Mirena hormonal IUD is the most commonly used form of birth control by Ob/Gyn's in the United States!!  This speaks highly to it's success and the freedom it offers!!

Warning Signs

These symptoms may signal there is a problem with your IUD. Call your doctor if you have any of the following symptoms:

  • Severe abdominal pain
  • Pain during sex
  • A missed period or other signs of pregnancy
  • Unusual vaginal discharge
  • A change in length or position of the string

Finally . . .

The IUD offers safe, effective, and reversible protection against pregnancy for many women. Weighing the benefits and risks of using an IUD, and knowing your medical and sexual history, will help you and your doctor decide whether this method of birth control is right for you.



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