The intrauterine device (IUD or IUCD) is made of plastic or metal or a combination of these materials. It is introduced into the endometrial cavity through the cervical canal. A large variety of shapes and sizes have been tried, with varying degrees of contraceptive effectiveness.
At the present time, only 3 IUDs are available for use in the U.S.: the Progestasert, the Copper TCu380A (Paragard), and a levonorgestrel-releasing system (Mirena) (
Fig 33-3). The Progestasert is made of a special polymer that contains a reservoir of 38 mg of progesterone, which is released at a rate of 65 g per day. However, due to this design, the useful lifespan of this device is only 1 year. The Paragard is wound with copper wire that creates a surface area of copper of 300 mm2 on the vertical arms and 40 mm2 on each of the transverse arms. The lifespan of this device is at least 10 years.
Recently, an intrauterine system containing levonorgestrel (released at 20 ug/d; Mirena) has been approved for use in the U.S. It provides contraception for up to 5 years. When compared to the copper TCu380A and Norplant, it was found to be just as effective for contraception but also more likely to cause amenorrhea, which in some patients is a benefit. Hormonal side effects such as depression, acne, headache, and weight change may also occur.
Just how IUDs act to prevent conception is not known. The most widely observed phenomenon is mobilization of leukocytes in response to the presence of the foreign body. The leukocytes aggregate around the IUD in the endometrial fluids and mucosa and, to a lesser extent, in the stroma and underlying myometrium. It is hypothesized that the leukocytes produce an environment hostile to the fertilized ovum. In laboratory animals, this leukocytic infiltration apparently is not dependent on microbial invasion. In human beings, the uterine cavity sterilizes itself, usually within 2-4 weeks after the device is inserted. Other theories regarding the mechanism of action are spermicidal activity with copper devices, disruption of endometrial maturation with the progesterone-releasing device, alteration of normal tubal cilial action, and even disruption of normal oocyte maturation. In short, the mechanism of action is not established. Furthermore, there are no data to suggest that a major mechanism of action may be that of an abortifacient.
Efficacy with the Paragard device is high, with a failure rate of less than 1% per year with prolonged use. In contrast, the Progestasert has a failure rate of about 1-1.5% with 25% of the pregnancies being ectopic. These data suggest that the latter device, unlike many contraceptive choices, offers no protection against extrauterine pregnancy.
It is felt by many practitioners that it is best to insert an IUD during a menstrual period because the cervical canal is fully patent then and the patient is least likely to be pregnant (
Fig 33-4). Furthermore, the endometrial cavity may be more distensible at this time in the cycle, and uterine cramps, if they occur as a result of insertion, will be less noticeable. However, insertion can be accomplished at any other time if this is desired or more convenient for the patient.
After a pelvic examination has shown that the external and internal genitalia are normal, an antiseptic is used to cleanse the cervix. A single-toothed tenaculum is then placed on the anterior lip of the cervix and gentle traction is applied. This traction tends to reduce the angle between the cervix and the fundus and facilitates introduction of the uterine sound.
After the direction and depth of the uterine cavity have been determined by means of the sound, the device is inserted with the aid of the appropriate insertion tube. Most inserters are equipped with a guide that indicates the direction and the plane in which the device will lie when it emerges from the insertion tube into the cavity. Currently available devices are freed within the uterine cavity by withdrawal of the insertion tube over the plunger rather than by being pushed out of the inserted tube and into the uterine cavity by the plunger. This withdrawal technique reduces the chances for perforation of the uterine wall.
Most IUDs have a monofilament plastic tail or strand that extends through the cervix so that the patient can feel the thread and thus be certain the device is staying in place. Moreover, the tail facilitates removal when desired.
Complications of Insertion
There may be moderate discomfort or pain when the uterus is sounded or when the IUD is inserted. In general, the larger the IUD, the more likely it is to cause pain. The pain and occasional syncopal reactions are due to dilatation of the cervical canal and distention of the endometrial cavity. Paracervical anesthesia is desirable, since both pain and syncope are significantly reduced. Mild analgesics may be helpful for several hours following IUD insertion.
Partial or complete perforation of the uterus is a rare complication of IUD insertion. It can be avoided by meticulous care in ascertaining the position and size of the uterus and by strict adherence to the recommended insertion procedure.
The presence of the IUD may elicit uterine cramps (an attempt by the uterus to rid itself of the device) for hours or days after insertion. With larger devices, the intensity of the cramps may require removal of the IUD.
If pregnancy occurs and the patient wishes it to continue, the IUD may be removed by traction on the plastic tail. If gentle traction does not effect prompt and easy removal, it is probably best to leave the device in place. However, the incidence of spontaneous abortion with a device in situ is about 50%, whereas the normal incidence is 12% or higher. Removal of the IUD reduces the risk of spontaneous abortion to about 20-25% and virtually eliminates the risk of septic abortion. In patients using the copper IUDs, the risk of ectopic pregnancy is reduced twofold or more relative to patients using no contraception. Although about 5% of the pregnancies that occur with a copper IUD in situ are ectopic, the overall contraceptive action of copper IUDs reduces the risk of all pregnancies and the absolute risk of an ectopic pregnancy. Data involving the Progestasert suggests that ectopic pregnancy protection does not occur with that device; there are even some data that indicate that the risk may be 50% or more greater in comparison with that of no contraception. In large trials of Mirena, half of all pregnancies during the study were ectopic, but the rate of ectopics with Mirena was not significantly different than the rate for sexually active women not using contraception. There is no increased incidence of congenital abnormalities in babies who are conceived with the IUD in utero.
Most spontaneous expulsions of IUDs occur in the first few months after their insertion - most frequently during menstruation. The incidence of expulsion varies with the stiffness, size, and shape of the device. In general, the expulsion rate is roughly proportional to the degree of distortion of the endometrial cavity brought about by the presence of the IUD. The patient should examine herself periodically, and routinely after her menses, to be assured that the tail of the device is still present, ie, that the device is in place. If the tail cannot be felt and the patient is unaware of having expelled the device, she should see her physician. Until her appointment, alternate contraception should be used. Expulsion may have gone unnoticed, the plastic filament may have been drawn back into the cervix or endometrial cavity, the device may have perforated the uterine wall at insertion and passed into the peritoneal cavity (< 1 out of 1000 insertions), or the tail may have separated from the device and been expelled unnoticed.
The correct explanation can be found by careful inspection or by exploration of the endometrial cavity with an ultrasound examination or, if necessary, by an x-ray examination that includes an anteroposterior as well as a lateral film and use of a sound to localize the uterine cavity. (All IUDs available in the U.S. are radiopaque because of their metallic components or because they have been impregnated with barium sulfate.)
C. Bleeding or Pain
Either bleeding or pain or both are common reasons for removal of an IUD and discontinuation of this method of contraception. As is the case with expulsions, the incidence of pain or bleeding is more or less proportional to the degree of endometrial compression and myometrial distention brought about by the IUD. Thus, an IUD that conforms to the natural size and shape of the endometrial cavity is likely to cause less pain or bleeding than one that distorts the cavity and the uterine wall. Nevertheless, bleeding may increase with the copper IUD, but decreases with Mirena.
D. Pelvic Infection
A number of epidemiologic studies have documented the association between IUD use and pelvic inflammatory disease or salpingitis. However, more recent studies that have controlled for risk factors associated with salpingitis have better clarified the extent of risk. It appears that the highest risk (3- to 4-fold increase) occurs around the time of insertion, suggesting that endometrial cavity contamination in the presence of a foreign body (the IUD) is the major mechanism. No evidence of an increased risk of salpingitis is found 3-4 months after insertion or thereafter in women who don’t have risk factors for STDs or salpingitis. In addition, it appears that women at risk for STDs, ie, those with multiple sexual partners or prior STDs, have a higher risk of infection than other women. However, a recent review of the literature indicates that the evidence concerning IUD-associated infection and infertility may be exaggerated.
Infection with Actinomyces israelii, an anaerobic, gram-positive bacteria, has been reported in association with IUD use. Most diagnoses have been made using the appearance of colonies on cervicovaginal Papanicolaou (Pap) smears due to the difficulty of culturing the organism. When A israelii is detected on PAP smear, antibiotic treatment is recommended (ampicillin, 250 mg four times a day for 14 days), and if the repeat PAP smear is positive, the IUD should be removed.
- Methods of contraception
Revision date: June 22, 2011
Last revised: by Tatiana Kuznetsova, D.M.D.