Definitions

intrauterine-device

Intrauterine device

An intrauterine device (intra meaning within, and uterine meaning of the uterus) is a birth control device placed in the uterus, also known as an IUD or a coil (this colloquialism is based on the coil-shaped design of early IUDs). Dr. Ernst Gräfenberg of Germany invented an early IUD and was the first person to market these devices. The IUD is the world's most widely used method of reversible birth control, currently used by nearly 160 million women (just over two-thirds of whom are in China where it is the most widely used birth control method, surpassing sterilization). The device has to be fitted inside or removed from the uterus by a doctor or qualified medical practitioner. It remains in place the entire time pregnancy is not desired. Depending on the type, a single IUD is approved for 5 to 10 years, and trials have demonstrated the copper T 380A to be effective for at least 12 years.

History

According to popular legend, Arab traders inserted small stones into the uteruses of their camels to prevent pregnancy during long desert treks. The story was originally a tall tale to entertain delegates at a scientific conference on family planning; although it was later repeated as truth, it has no known historical basis.

Precursors to IUDs were first marketed in 1902. Developed from stem pessaries (where the stem held the pessary in place over the cervix), the 'stem' on these devices actually extended into the uterus itself. Also known as interuterine devices (because they occupied both the vagina and the uterus), they had high rates of infection and were condemned by the medical community.

The first intrauterine device (contained entirely in the uterus) was described in a German publication in 1909, although the author appears to have never marketed his product.

In 1929, Dr. Ernst Gräfenberg of Germany published a report on an IUD made of silk suture. He had found a 3% pregnancy rate among 1,100 women using his ring. In 1930, Dr. Gräfenberg reported a lower pregnancy rate of 1.6% among 600 women using an improved ring wrapped in silver wire. Unbeknownst to Dr. Gräfenberg, the silver wire was contaminated with 26% copper. Copper's role in increasing IUD efficacy would not be recognized until nearly 40 years later.

In 1934, Japanese physician Tenrei Ota developed a variation of the Gräfenberg ring that contained a supportive structure in the center. The addition of this central disc lowered the IUD's expulsion rate. These devices still had high rates of infection, and their use and development was further stifled by World War II politics: contraception was forbidden in both Nazi Germany and Axis-allied Japan. The Western world did not learn of the work by Gräfenberg and Ota until well after the war ended.

The first plastic IUD, the Marguiles Coil or Marguiles Spiral, was introduced in 1958. This device was somewhat large, causing discomfort to a large proportion of women users, and had a hard plastic tail, causing discomfort to their male partners. The Lippes Loop, a slightly smaller device with a monofilament tail, was introduced in 1962 and gained in popularity over the Marguiles device.

The stainless steel single-ring IUD was developed in the 1970s and widely used in China because of low manufacturing costs. The Chinese government banned production of steel IUDs in 1993 due to high failure rates (up to 10% per year).

Dr. Howard Tatum, in the USA, conceived the plastic T-shaped IUD in 1968. Shortly thereafter Dr. Jaime Zipper, in Chile, introduced the idea of adding copper to the devices to improve their contraceptive effectiveness. It was found that copper-containing devices could be made in smaller sizes without compromising effectiveness, resulting in fewer side effects such as pain and bleeding. T-shaped devices had lower rates of expulsion due to their greater similarity to the shape of the uterus.

The poorly designed Dalkon Shield plastic IUD (which had a multifilament tail) was manufactured by the A. H. Robins Company and sold by Robins in the United States for three and a half years from January 1971 through June 1974, before sales were suspended by Robins on June 28, 1974 at the request of the FDA because of safety concerns following reports of 110 septic spontaneous abortions in women with the Dalkon Shield in place, seven of whom had died. Robins stopped international sales of the Dalkon Shield in April 1975.

Second-generation copper-T IUDs were also introduced in the 1970s. These devices had higher surface areas of copper, and for the first time consistently achieved effectiveness rates of greater than 99%. Worldwide today, with the exception of the new GyneFix, this is the only type of non-hormonal IUD available.

Types of IUDs

There are two broad categories of intrauterine contraceptive devices: inert and copper-based devices, and hormonally-based devices that work by releasing a progestogen.

In the United States, there are two types of intrauterine contraceptive available: the copper Paragard and the hormonal Mirena. Both of these contraceptives are referred to as IUDs.

In the United Kingdom, where seven types of copper-containing IUDs are available, the term IUD only refers to inert or copper-containing devices. Hormonal intra-uterine contraceptives are considered a different form of contraception from copper IUDs, and they are distinguished with the term IntraUterine System or IUS.

Most non-hormonal IUDs have a plastic T-shaped frame that is wound around with pure electrolytic copper wire and/or has copper collars (sleeves). The Paragard T 380a is 32 mm (1.26") in the horizontal direction (top of the T), and 36 mm (1.42") in the vertical direction (leg of the T). In some IUDs, such as the Nova T 380, the pure copper wire has a silver core which has been shown to prevent breaking of the wire. The arms of the frame hold the IUD in place near the top of the uterus. The GyneFix does not have a T-shape, but rather is a loop that holds several copper tubes. The GyneFix is held in place by a suture to the fundus of the uterus. All copper-containing IUDs have a number as part of their name. This is the surface area of copper (in square millimeters) the IUD provides.

Hormonal intra-uterine devices

Hormonal uterine devices do not increase bleeding as inert and copper-containing IUDs do. Rather, they reduce menstrual bleeding or prevent menstruation altogether, and can be used as a treatment for menorrhagia (heavy periods).

Although use of IntraUterine Systems results in much lower systemic progestogen levels than other very-low-dose progestogen-only hormonal contraceptives, they might possibly have some of the same side effects.

Progestasert was the first hormonal uterine device, developed in 1976 and manufactured until 2001. It released progesterone, was replaced annually, and had a failure rate of 2% per year.

As of 2007, the LNG-20 IUS - marketed as Mirena by Bayer - is the only IntraUterine System available. First introduced in 1990, it releases levonorgestrel (a progestogen) and may be used for five years.

A lower-dose T-shaped IntraUterine System named Femilis is being developed by Contrel, a Belgian company. Contrel also manufactures the FibroPlant-LNG, a frameless IUS. FibroPlant is anchored to the fundus of the uterus as the GyneFix IUD is. Although a number of trials have shown positive results, FibroPlant is not yet commercially available.

Contraindications

The WHO Medical Eligibility Criteria for Contraceptive Use and RCOG Faculty of Family Planning & Reproductive Health Care (FFPRHC) UK Medical Eligibility Criteria for Contraceptive Use list the following as conditions where insertion of a copper IUD is not usually recommended (category 3) or conditions where a copper IUD should not be inserted (category 4):

Category 3. Conditions where the theoretical or proven risks usually outweigh the advantages of inserting a copper IUD:

Category 4. Conditions which represent an unacceptable health risk if a copper IUD is inserted:

Some concern has been expressed that women with metal sensitivities to copper or nickel may experience adverse reactions from an IUD. The metal used in IUDs is 99.99% copper, with one study finding a maximum nickel content of 0.001%. Because nickel has a relatively high sensitizing potential, a few researchers suggested even this tiny amount might be problematic. A few case reports have attributed eczematous dermatitis and urticaria in a handful of users of copper-releasing IUDs to systemic copper or nickel allergic contact dermatitis. However, the daily metal absorption from an IUD is only a fraction of the normal daily absorption from food, and many dermatologists are skeptical that the symptoms described in the case reports were actually caused by metal sensitivity.

While nulliparous women (women who have never given birth) are somewhat more likely to have side effects, this is not a contraindication for IUD use.

Some doctors prefer to insert the IUD during menstruation to verify that the woman is not pregnant at the time of insertion. However, IUDs may safely be inserted at any time during the menstrual cycle as long as it is reasonably certain the woman is not pregnant. Insertion may be more comfortable if done midcycle, when the cervix is naturally dilated.

Side effects and complications

Insertion of the IUD may introduce bacteria into the uterus. The insertion process carries a small, transient increased risk of pelvic inflammatory disease in the first 20 days following insertion. It is very important that the provider use proper infection-prevention techniques during insertion. Antibiotics should be given before insertion to women at high risk for endocarditis (infection of the valves within the heart), but should not be used routinely.

During the placement appointment, the cervix is dilated in order to sound (measure) the uterus and insert the IUD. Cervix dilation is uncomfortable and, for some women, painful. Doctors often advise women to take painkillers before the procedure to reduce discomfort, and some will use a local anaesthetic.

After IUD insertion, menstrual periods are often heavier, more painful, or both - especially for the first few months after they are inserted. On average, menstrual blood loss increases by 20–50% after insertion of a copper-T IUD; increased menstrual discomfort is the most common medical reason for IUD removal.

Complications include expulsion and uterine perforation. Uterine perforation is generally caused by an inexperienced provider and is very rare. Expulsion is more common in younger women, women who have not had children, and when an IUD is inserted immediately after childbirth or abortion. Women should check the string of the IUD at least once per menstrual cycle to verify that it is still in place.

The string(s) may be felt by some men during intercourse. If this is problematic, the provider may cut the strings even down to the cervix, so they cannot be felt. Shortening the strings does prevent the woman from checking for expulsion, however.

The risk of ectopic pregnancy to a woman using an IUD is lower than the risk of ectopic pregnancy to a woman using no form of birth control. However, of pregnancies that do occur during IUD use, a higher than expected percentage (3–4%) are ectopic.

The pregnancy rate during IUD use is very low (less than 1% per year). If pregnancy does occur, the IUD should be removed. Although IUDs are not teratogenic, presence of the IUD increases the risk of miscarriage, particularly during the second trimester. It also increases the risk of premature delivery. Although the Dalkon Shield IUD was associated with septic abortions (infections associated with miscarriage), other brands of IUD are not. IUDs are also not associated with birth defects or other pregnancy complications.

Non-hormonal (copper) IUDs are considered safe to use while breastfeeding.

Effectiveness and mechanism of contraception

All second-generation copper-T IUDs have failure rates of less than 1% per year, and cumulative 10-year failure rates of 2-6%. A copper IUD may also be used as emergency contraception. If an IUD is inserted within five days of unprotected intercourse, a woman's risk of pregnancy is reduced to that of ongoing IUD users.

A large World Health Organization trial reported a cumulative 12-year failure rate of 2.2% for the T 380A (ParaGard) (an average failure rate of 0.18% per year over 12 years), equivalent to a cumulative 10-year failure rate of 1.8% following tubal ligation. The frameless GyneFix also has a failure rate of less than 1% per year. Worldwide, older IUD models with lower effectiveness rates are no longer produced.

The presence of a device in the uterus prompts the release of leukocytes and prostaglandins by the endometrium. These substances are hostile to both sperm and eggs; the presence of copper increases this spermicidal effect.

When used as ongoing contraception, the primary mechanism of action of the IUD is spermicidal/ovicidal. However, post-fertilization mechanisms are believed by some physicians to contribute significantly to their effectiveness, and may be a primary mechanism when the IUD is used as emergency contraception. Because many pro-life individuals and organizations define fertilization as the beginning of pregnancy, this possible secondary mechanism of action has led some pro-life individuals and organizations to label the IUD an abortifacient. More recent analysis indicates that IUD operate earlier in the reproductive process than was previously thought. Since IUD prevent "chemical pregnancies," tubal flushing studies do not find fertilized eggs in women using IUD, and IUD markedly reduces the rate of ectopic pregnancies, Contraceptive technology concludes that IUD prevent fertilization.

Some barrier contraceptives protect against STDs. Hormonal contraceptives reduce the risk of developing pelvic inflammatory disease (PID), a serious complication of certain STDs. IUDs, by contrast, do not protect against STDs or PID.

Use as emergency contraception

Intrauterine devices can be used as emergency contraception to prevent pregnancy up to 5 days after unprotected sexual intercourse, or sexual intercourse during which the primary contraception is believed to have failed (e.g. a condom was used, but it broke). Insertion of a copper-T IUD as emergency contraception is more than 99% effective, making it more effective than emergency contraceptive pills (ECP or 'morning-after pill').

Prevalence

The IUD is the world's most widely used method of reversible birth control, currently used by nearly 160 million women (just over two-thirds of whom are in China where it is the most widely used birth control method, surpassing sterilization). Usage in many countries has been measured by surveys of married women of reproductive age. In this population in the early 1990s, IUD use ranged from 1.5% in North America, to 18% in Scandinavia, 33% in Russia and China, and 40% in Kazakhstan. Use in China increased to 45% of married women by 2002.

Among women who recently had sex and are not trying to become pregnant, 1.9% use IUDs in the United States, 6% in the United Kingdom and 20% in France.

In the U.S., the ParaGard T 380A was approved by the FDA in 1984 and became available for use in 1988. It is still the only copper IUD approved for use in the U.S., and was used by 1.3% of women of reproductive age in a 2002 U.S. survey. A wider variety of IUDs are available outside of the U.S. In the U.K., for example, seven brands are available: Flexi-T 300, Multi-Safe 375, Multi-Load Cu 375, Neo-Safe T380, Nova T 380, T-Safe 380A, and GyneFix - also called FlexiGard 330 or CuFix PP330.

See also

References

External links

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