Intrauterine device

An intrauterine device (IUD) is more than 99% effective in preventing pregnancy, so that only 1 out of 100 sexually active women who use an IUD will get pregnant in a year, and if inserted within five days of unprotected sex, it still works. An IUD is a 1- to 2-inch piece of flexible plastic shaped like a T that is installed by a doctor into a woman's uterus, where it remains until removed (possibly years later) and prevents implantation of a fertilized egg. An IUD can be used by a woman even if she cannot tolerate the side effects of pills and patches.

As of 2023, there are 5 brands of IUDs that are FDA-approved for use in the United States:

• Paragard
• Mirena
• Kyleena
• Liletta
• Skyla

Clinical practice guidelines address management. Barrier methods rely on consistent, technically correct use to be effective, so their typical failure rates in practice are higher than they would be with perfect compliance. By contrast, the IUD has similar rates of failure for both typical and perfect use. First year failure rates are less than 1% for the copper T 380A IUD and 2% for the progesterone-releasing IUD.

Unlike cervical caps and diaphragms, which are placed into the vagina by the user, the IUD is placed into the hollow uterus by the health care provider. The inside of the uterus is an internal body cavity, and is not accessible except by a health care provider. Placement of the IUD usually is performed in the office or clinic, and requires the dilation of the normal opening of the cervix (cervical os). The procedure is uncomfortable for the woman, and there is a risk of contaminating the interior of the womb. In most IUDs, there is a string that exits the uterus through the cervical os and can be felt in the vagina. Although placing an IUD is a medical procedure rather than a surgical procedure, it is a skilled procedure that must be carried out in a clean environment.

IUDs are spontaneously expelled from the uterus in many cases, and once expelled, no longer provide protection. The rate of expulsion is related to the position of insertion, and is lowest when an experienced and skillful clinician places the device high in the fundus of the uterus. Expulsions are most common during the first year after insertion, and the rate of pregnancy decreases after this first year. With some devices, the cumulative risk of pregnancy over a decade is less than 2%. With long-term placement, the annual incidence of side effects such as excessive bleeding or cramping also decreases.

"Contemporary IUDs rival tubal sterilisation in efficacy and are much safer than previously thought." However true that may be, IUDs have been associated with a higher rate of fallopian tube occlusion and resultant infertility. Many gynecologists recommend the use of IUDs as being nearly ideal for older women, especially for those women who have a low risk of contracting a sexually transmitted infection and those who have substantially finished childbearing. . Copper-containing IUDs appear not to entail significant risk of copper toxicity, as neither serum nor urine copper levels increase, suggesting non-absorption of copper from intrauterine fluid.

Progesterone-containing IUDs do not appear to be spermicidal. Although the overall rate of pregnancy is much lower in women with these IUDs than in control groups not using contraception, the rate of ectopic pregnancy is higher in the progesterone-containing IUD group than in the 'no-contraceptive' group. The reduced rate of pregnancy is therefore most likely due to reduced implantation of fertilized ova rather than reduced fertilization of ova. In other words, progesterone-containing IUDs appear to work mostly by preventing normal pregnancy from ever being established in the uterus rather than by preventing conception.

IUD insertion as an emergency contraceptive

Emergency contraception is the use of a drug or device to prevent pregnancy after unprotected intercourse. Placement of an IUD is one form of emergency contraception. It is generally recommended that IUDs be avoided in women who are at high risk of sexually transmitted infections; in women with these infections, especially Chlamydia, there is a much higher rate of pelvic inflammatory disease with an onset soon after insertion of the IUD. Although this disease is treatable with antibiotics, it results in a significant rate of complications, including permanent infertility. Because IUDs are contraindicated as an emergency contraceptive when there is a significant risk of a sexually transmitted disease, this is not a method recommended for emergency contraception after rape.

Side effects and complications

Bleeding is the main reason that women who seek to have IUDs removed do so, either because of prolonged, excessive or inter-menstrual bleeding (bleeding between periods). Perforation of the device through the uterine wall does occur, and although most often is not a serious complication, rarely can cause an acute abdomen from peritonitis that requires emergency surgery. The small risk of pelvic inflammatory disease associated with IUDs is limited to the first few weeks after insertion.

Mirena, the levonorgestrel-releasing intrauterine system may or may not contribute to decreased bone mineral density. The two negative studies are small and limited to measurements of bone-mineral density at the forearm. The positive study is a single case report.

Pregnancy rates after IUD removal

In previous decades, the common wisdom among health scientists and women using contraceptives was that IUDs were generally associated with a high risk of permanent sterility from fallopian tube obstruction caused by pelvic inflammatory disease. However, the risk of pelvic inflammatory disease with the IUD is now said to be small, except in those women who have a sexually transmitted disease (particularly chlamydia), at the time that the IUD is inserted. One way to evaluate the risk of IUDs in this regard is to study the pregnancy rates of women who have had IUDs in place as a birth control method, after removal. If IUDs are indeed associated with a high risk of pelvic inflammatory disease generally, then these pregnancy rates should be reduced as compared to controls. This has not been the case, generally, after IUDs are removed; women who have had them are able to get pregnant at the same rates as women the same age who have not had IUDs.