The intrauterine device (IUD) is a method of birth control designed for insertion into a woman's uterus so that changes occur in the uterus that make it difficult for fertilization of an egg and implantation of a pregnancy.
IUDs also have been referred to as "intrauterine contraception (IUC). IUDs approved for use in the U.S. contain medications that are released over time to facilitate the contraceptive effect.
The IUD is a small "T"-shaped device with a monofilament tail that is inserted into the uterus by a health care practitioner in the office setting. When inserted into the uterus, the arms of the "T" are folded down, but they then open out to form the top of the "T". The device rests inside the uterus with the base of the T just above the cervix and the arms of the T extending horizontally across the uterus. A short piece of monofilament string attached to the IUD extends through the cervix into the vagina. This string makes it possible to be sure that the IUD is still in the uterus.
Although IUDs are highly effective, no birth control method, except abstinence, is considered to be 100% effective.
How does an IUD work?
It is not fully understood how IUDs work. They are thought to prevent conception by causing a brief localized inflammation that begins about 24 hours after insertion. This causes an inflammatory reaction inside the uterus that attracts white blood cells. The white blood cells produce substances that are toxic or poisonous to sperm. The progesterone-releasing IUDs also cause a subtle change in the endometrial environment that impairs the implantation of the egg in the uterine wall. This type of IUD also alters the cervical mucus, which, in turn, inhibits sperm from passing through the cervix.
IUDs are only available by prescription and must be properly inserted by a health care professional. A pelvic exam is required to insert an IUD. The IUD is inserted into the uterus long as she is not pregnant.
The woman must check her IUD every month to be sure that it is still in place. The woman with an IUD in place will still have normal menstrual periods, although some women notice that flow is heavier. Other women, especially those with a hormone-releasing IUD, may have lighter flow. Sometimes, the uterus expels (pushes out) the IUD. Expulsions may not cause any specific symptoms and can be overlooked. In addition to the woman checking the IUD, the device must also be checked periodically by a health-care professional.
Risks and Complications
An IUD may not be appropriate for women who have heavy menstrual bleeding, had previous pelvic infections, have more than one sexual partner, or plan on getting pregnant. This is because IUDs do not protect against sexually transmitted infections (STDs) and should not be in place if a woman intends to become pregnant.
If women become pregnant with their IUDs in place, 50% of the pregnancies end in miscarriage. Any woman with an IUD who develops signs or symptoms of pregnancy, or has a positive pregnancy test, should see her health-care professional right away.
Women who use non-progesterone types of IUDs are less likely to have an ectopic pregnancy compared to women using no contraception. When a woman using an IUD does become pregnant, the pregnancy is more likely to be ectopic, but still ectopic pregnancy in a user of an IUD is a rare occurrence.
Serious complications due to infection (pelvic inflammatory disease) associated with an IUD may prevent a woman from being able to become pregnant in the future.
Also, with the progesterone-releasing IUDs (levonorgestrel IUDs), a reduction in menstrual flow and a decrease in painful menstrual cramping are often observed with continued use. This is because the progesterone hormone can cause thinning of the lining of the uterus. These menstrual changes are not dangerous in any way and do not mean that the contraceptive action of the IUD is diminished.
The IUD provides no protection against sexually transmitted diseases (STDs).
How is an IUD removed?
An IUD must be removed by a health care professional.
It is very important that a woman not attempt to remove an IUD on her own, as serious problems may result. IUD removal is carried out by determining the position of the uterus, then locating and grasping the stings of the IUD with a special forceps or clamp. The health care professional will then remove the IUD by gentle traction on the strings.
Occasionally, the strings of the IUD will not be located. In these situations, the strings have often slipped higher into the cervical canal. Your health care professional can use special instruments to locate the strings and/or remove the IUD. Complications of IUD removal are rare, and removal can take place at any time. Some studies have shown that removal is easier during the menstrual period, when a woman's cervix is typically softer, than during other times in the menstrual cycle.