Intrauterine Devices


Intrauterine devices (IUDS) are very important worldwide but play a minor role in contra ception for the U.S. population because of a fear of infection that is no longer justified. Cop per IUDs provide safe, long-term contraception with effectiveness equivalent to tubal ster ilization. Hormone-releasing IUDs need to be replaced every year. Two IUDs are available in the U.S.: the Copper T380 (Paraguard) and the progesterone-releasing T (Progestasert). The Copper T380 has bands of copper on the cross arms of the T in addition to copper wire around the stem, providing a total surface area of 380 mm of copper, almost double the sur face area of copper of earlier copper devices. The copper T380 is approved by the U.S. Food and Drug Administration (FDA) for up to 10 years of continuous use.


Mechanism of Action Intrauterine devices cause the formation of a biological foam within the uterine cavity that contains strands of fibrin, phagocytic cells, and proteolyte enzymes Copper IUDs continuously release a small amount of the metal, producing un even greater inflammatory response. All IUDs stimulate the formation of prostaglandi within the uterus, consistent with both smooth muscle contraction and inflammation Scanning electron microscopy studies of the endometrium of women wearing IUDs show u lerations in the surface morphology of cells, especially of the microvilli of ciliated cells. There are major alterations in the composition of proteins within the uterine cavity and new proteins and proteinase inhibitors are found in washings from the uterus, The allered intrauterine environment interferes with sperm passage through the uterus, pre venting fertilization.


The IUD is not an abortifacient. The contraceptive effectiveness does not depend on inter ference implantation, but this place and occurs and is the bonus for uiving copper IUDs for emergency contraception. Sperm can be obtained via laparoscopy in washings from the fallopian tubes of control women, ut midcycle, whereas to sperm present in the tubal washings from women wearing IUDs Ova flushed from the tubes at tobal sierilization showed no evidence of fertilization in women wearing IUDs , and studies of serum B-human chorionic gonadotropin (hCG) do not indicate pregnancy in women weaning IUDS.


The progesterone-releasing IUD contains natural progesterone in its stem inside a polymer capsule that allows sustained, slow release of hormone. It is approved for I year of use. This produces un atrophic endometrial lining. AT device that releases the more potent progestin, norgestrel, is available in Europe. It produces high local con centrations of the progestin in the uterine cavity and produces blood levels about one-half those seen with the levonorgestrel implant, which are sufficient to inhibit ovulation in some women.


Effectiveness The Copper T380 and the fevonorgestrel 'T have remarkably low pregnancy rates, less than 0.2 per 100 women years. Total pregnancies over a 7-year period were only 1.1 per 100 for the levonorgestrel T and 1 4 for the Copper T380 in a comparative study. The Progestasert has a higher failure rate, about three per 100 women per year.


Infection The Women's Health study found the Dalkan Shield device (now withdrawn from the market) to increase the risk of pelvic inflammatory disease (PID) by eightfold when women hospitalized for PID were compared to control women hospitalized for other illnesses. In contrast, risk from the other IUDs was markedly less: relative risk of PID was 2.2 for the Progestasert. 1.9 for the Copper 7, 1.3 for the Saf-T-Coil, and 1.2 for the Lippes Loop. Increased risk was detectable only within 4 months of insertion of the IUD. A still larger, prospective World Health Organization Study revealed that PID increased only during the first 20 days after insertion. Thereafter, the rate of diagnosis of PID was about 1.6 cases per 1000 women per year, the same as in the general population.


Exposure to sexually transmitted pathogens is a more important determinant of PID than the wearing of an IUD. In the Women's Health Study, women who were currently married or cohabiting and who said they had only one sexual partner in the past 6 months had no increase in PID. In contrast, previously married or single women had marginal in crease in risk, even though they had only one partner in the previous 6 months. The only pelvic infection that has been unequivocally related to IUDS is actinomycosis . It appears that PID with actinomycosis has been reported only in women wearing IUDS Rates of colonization with actinomycosis increase with duration of use for plastic devices but appear to be much less for copper-releasing IUDS.


Management of PID When PID is suspected in an IUD-wearing woman, the IUD should be immediately removed, appropriate cultures should be taken, and high-dose an tibiotic therapy should be started. Pelvic abscess should be suspected and ruled out by ultrasound examination.


Ectopic Pregnancy If pregnancy occurs in an IUD wearer, it will be ectopic in about 5% of cases. This is because the fallopian tubes are less well protected against pregnancy than the uterus. Compared with women using no contraception, however, women wearing ei ther the Copper T380 or the levonorgestrel T have an 80-90% reduction in the risk of ec topic pregnancy , which is a greater reduction than that seen for users of barrier meth ods. Women using oral contraceptives have a 90% reduction of risk . In contrast, the Progestasert increases risk slightly, probably because the progesterone affects tubal motility and does not inhibit ovulation.


Fertility Case-control studies of infertile women in the U.S. have revealed that a history of IUD use is associated with a twofold increase in the risk of tubal infertility. The risk ap plies to methods other than the copper IUD, for which there is no increased risk. Risk was not increased among women who reported only one sexual partner. The Ox ford Study found that women gave birth just as promptly after IUD removal as they did af ter discontinuing use of the diaphragm. Exposure to sexually transmitted pathogens confers risk for infertility. Modern IUDs are, at most, a small risk factor.

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