Intrauterine Device (IUD)

What is an IUD?
The intrauterine device (IUD) is a plastic device that is put into the uterus to prevent pregnancy. There are two kinds used in the United States. One contains copper wire and the other an artificial women's hormone (a progestin) called levonorgestrel. The copper IUD may remain in the uterus for 10 years. The progestin IUD must be replaced after 5 years when much of the hormone has been used. Both of the IUDs are "T" shaped.

How Does it Work?
There are several theories on how IUDs work, but no one knows for sure. The IUD may prevent fertilization (the joining of the egg and sperm) or it may prevent the fertilized egg from implanting and growing on the wall of the uterus. Here are some of the theories:

  • There may be increased movement (muscle contractions) in the uterus and uterine tubes and that may prevent fertilization or implantation
  • There may be an inflammatory response which prevents fertilization or implantation.
  • There may be increased numbers of white blood cells from the imflammation (and also from progestin in the progestin IUD) which destroy sperm and the fertilized egg.
  • Progestin prevents the growth of the lining of the uterus. It also causes cervical mucus to be thicker which decreases sperm movement. It also contains many white blood cells that destroy sperm.
  • Copper may decrease sperm movement, ability to combine with the egg, and it also destroys sperm.
  • There may be increased production of prostaglandins that may interfere with implantation.

How effective are IUDs?
Effectiveness depends on whether the woman checks for placement of the IUD string at the cervical opening. Women who check the string every time before intercourse will have higher effectiveness rates. Both theoretical and use effectiveness rates of the two newer IUDs are greater than 99%.

IUDs are more likely to be expelled from the uterus in the first 3 months after insertion.

How is the IUD put into the uterus?
IUDs should be inserted during a menstrual period. It is more comfortable because the cervix (the neck of the uterus which is in the vagina) is softer and the cervical os (its mouth or opening) is more open at that time. Also, women are much less likely to be pregnant if they are having a period.

Most women feel some cramping during insertion of the IUD and for several minutes after insertion. Some report cramping for a day or two after and sometimes during the first few menstrual periods.

Complications of IUD use

Pelvic Inflammatory Disease (PID)
PID is an infection of the uterus and sometimes of the tubes, ovaries, and even the abdominal cavity. The risk of PID is much lower if you and your partners have no other partners. If you suspect that you may have a sexually transmitted infection (STI), like gonorrhea or chlamydia, see a health care provider immediately for treatment. It is important to be tested for STIs at least once a year or whenever you suspect that you may have been exposed. Symptoms of PID are a foul smelling discharge, pelvic pain or tenderness, severe cramping, or a fever.

PID can cause scarring of the uterine tubes which can lead to the inability to have children or an increased chance of having a pregnancy in the tube. The tube ruptures around 8 to 12 weeks of a pregnancy. This may result in severe bleeding which can cause death.

PID can cause chronic pelvic pain from scarring in the abdominal cavity. The infection alone can also result in death if the woman is not put on antibiotics soon enough.

Embedding or perforation
The IUD can work its way partly through, or all the way through the uterine wall. There may or may not be pain as this is happening. Guard against this by checking for the string before intercourse, or at least once a month.

The health care practitioner may injure the uterine wall during insertion. The injury may go all the way into the abdominal cavity. This is also called perforation. The perforation will heal, usually needing no treatment.

Expelling the IUD
A woman's uterus sometimes contracts and pushes the IUD out. This is more likely to happen in the first 3 months of use. There may be vaginal discharge and pain or lengthening of the string. Or there may be no indications that this is happening. It is very important to check for the string regularly.

Pregnancy with an IUD in place
If a pregnancy does occur, there is a 50% chance that the woman will have a miscarriage. She is at higher risk for infection with the IUD in place. If the IUD is removed, there is a 25% chance of a miscarriage.

Getting pregnant after removal of an IUD
It is best to wait at least 3 months after having an IUD removed to try to get pregnant. The uterine lining needs time to return to normal functioning and it may decrease the risk of an ectopic pregnancy.

Benefits of the progestin IUD - Mirena
This IUD releases 20 micrograms of progestin a day. Studies have shown:

  • Lighter periods with less cramping and bleeding - up to 88% less blood loss
  • Decreased bleeding at menopause - may avoid hysterectomy
  • Decreased growth of uterine lining with estrogen replacement therapy
  • Decreased pelvic infections, therefore, fewer ectopic pregnancies

Side effects of the progestin IUD - Mirena

  • no periods
  • acne
  • headaches
  • nausea
  • breast tenderness

Contraindications to getting an IUD
You should not have an IUD if you:

  • Are pregnant
  • Have PID or a history of PID
  • Have endometriosis
  • Have been exposed to or have gonorrhea or chlamydia
  • Have confirmed or suspected cancer of the cervix or uterus
  • Undiagnosed abnormal vaginal bleeding
  • Blood clot or bleeding disorder
  • Acute liver disease
  • Have abnormalities of the uterus such as those present from birth or possibly fibroids
  • Consider another birth control method if:
  • You have more than one partner or a partner with more than one partner
  • You are unable to check the IUD string, especially if your partner is also unable to check the string

IUDs Currently Available (In the United States)

Copper T380A, brand name: ParaGuard Intrauterine Copper Contraceptive
Manufacturer: Ortho-McNeil Pharmaceutical, Raritan, New Jersey

Progestin IUD, Brand name: Mirena Legonorgestrel-Releasing Intrauterine System
Manufacturer: Berlex Laboratories, Montville, New Jersey

American Health Consultants, Contraceptive Technology Update, Vol. 23, No. 4, April 2002.
Boston Women's Health Book Collective, Our Bodies, Ourselves, Simon & Schuster, 1998.
Hatcher, R., et al., Contraceptive Technology, 17th edition, Irvington Publishers, 1999.
Contraceptive Technology Seminar, San Francisco, California, 2001.

*Revised 12-2005 TM