Intrauterine Contraception
Jennifer E. Kaiser, MD, MSCI
David K. Turok, MD, MPH
Nomenclature
For consistency throughout this chapter authors use the term “intrauterine device (IUD)” when referring generically to all intrauterine methods of contraception. We acknowledge intrauterine contraceptive nomenclature can be confusing. For the subset of hormone-releasing devices, we use the term intrauterine system (IUS) to distinguish them and their resultant cervical mucous thickening from others.
Over 200 million women worldwide use intrauterine contraceptives (Table 6.1). All currently available IUDs were not marketed prior to 1988. In the United States, IUD use with older products peaked in the mid-1970s with around 2.5 million users, representing about 10% of all contraceptors. These rates declined rapidly through the 1980s, falling by two thirds from 1982 (7.1%) to 1988 (2.0%), reaching a nadir of 0.8% of contraceptive users in 1995.4 With the introduction of the first levonorgestrel (LNG) IUS in 2000, their popularity in the United States has grown considerably.6,7 By 2014, 12% of contracepting women used an IUD, and the rate is still climbing.5 New safety data over the past two decades have driven enthusiasm among reproductive health professionals. The favorable effects on bleeding patterns seen with the new LNG devices and growing interests
in nonhormonal methods, like copper IUDs, has contributed to greater acceptance by women.
in nonhormonal methods, like copper IUDs, has contributed to greater acceptance by women.
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IUDs provide women with the ability to reversibly control their fertility for years following a single placement during a simple office procedure. Current options include the hormone-free copper IUD and LNG IUS; the latter results in significant reductions in menstrual blood loss and discomfort.
Fewer than 1 in 100 women using a modern IUD over many years will experience pregnancy, and unlike short-acting methods like the pill, this success is not altered by user characteristics that affect compliance. Data from the CHOICE study and the Colorado Family Planning initiative (see Chapter 1) demonstrate that offering no cost availability of IUDs increases uptake and improves outcomes. While these data support offering IUDs to all women, clinicians should also recognize that acceptance or continuation of an IUD requires an active choice by the individual. We support a reproductive justice-centered approach to contraceptive counseling and recommendation of IUDs that empowers woman to choose the best method and timing of use for her instead of placing undue emphasis on methods and times deemed “best” by the medical profession.8,9 No woman should experience coercion to accept or continue with use of an IUD.
History of Modern IUDs
The use of IUDs has a long and colorful history.10 See the supplemental history chapter for details. Enthusiasm for the first oral contraceptive pills led to the introduction of a variety of mostly inert plastic IUDs of various designs with general good performance and acceptability.
Jaime Zipper of Chile initially suggested the addition of copper to the IUD. His experiments with metals indicated that copper acted locally on the endometrium.11 Howard Tatum in the United States combined Zipper’s suggestion with the development of the T shape to diminish the uterine reaction to the structural frame and produced the copper T. The addition of copper conferred several benefits: (1) the device could be smaller than inert IUDs and still provide effective contraception, (2) a spermicidal effect that resulted in an increase in contraceptive efficacy, and (3) a decrease in removals for pain and bleeding due to the reduction in the size and structure of the frame. The Cu-7 with a copper wound stem was developed in 1971 and quickly became the most popular device in the United States.
In 1970, AH Robbins introduced the Dalkon Shield, a small plastic device and promoted use of the product in young nulliparous women. Within 3 years, reports of serious pelvic infections began to appear in the literature prompting widespread concern about the overall safety of IUDs. These concerns eroded consumer and health care provider confidence in IUD safety and led to a significant decline in IUD use and the withdrawal of all but one device (ProgestasertTM) from the United States (U.S.) market by the mid-1980s.
We must credit the efforts of investigators who worked to point out the unique problems with the Dalkon Shield and reestablish the overall safety of IUDs that led to the current renaissance in use. Tatum and colleagues12 pointed out that a serious design flaw (a multifilament removal thread) of the Shield predisposed women to the risk of pelvic infection. Lee and colleagues13 published the first study that compared PID risk among IUD users to an appropriate control group using nonhormonal methods. They found an increased risk (RR = 8.3, 95% CI = 4.7 to 14.5) of PID confined to Dalkon Shield users, with risk for other devices small and isolated to the first 4 months following placement. In a landmark case-control study assessing infectious antibodies, Hubacher et al.14 showed that the risk of tubal infertility in nulliparous women was not associated with prior use of a copper IUD.
Although both the Cu-7 and the Tatum-T were withdrawn from the U.S. market in 1986 by G. D. Searle and Company in response to the Dalkon Shield controversy, IUD development continued. More copper was added to the Tatum-T frame by Population Council investigators, leading to the TCu380A (380 mm2 of exposed copper surface area) with copper wound around the stem plus a copper sleeve on each horizontal arm.15 The “A” in TCu380A is for “arms,” indicating the importance of the copper sleeves. Making the copper solid and tubular increased effectiveness and the lifespan of the IUD. The TCu380A has been in use in more than 30 countries since 1982, and in 1988, it was marketed in the United States as Paragard®.
Although bleeding profiles improved with a smaller device, the copper IUD did not solve the issue of heavy uterine bleeding. In an effort to decrease uterine bleeding, Dr. Tapani Luukkainen developed a long-acting progestin-releasing system by replacing the copper on a Nova-T copper IUD with LNG to create the first LNG-IUS, the Nova-T LNG.16 This LNGIUS, containing LNG 52 mg, was first approved in Europe in 1990 for a 5-year duration. In the United States, it was introduced and marketed as the Mirena® IUS in 2000 by Berlex. Since that time, Bayer acquired Mirena and has developed smaller, lower-dose LNG-containing IUSs (Kyleena®, Skyla/Jaydess®). In addition, Medicines360, a nonprofit company, brought an LNG-IUS product of the same size and dose as Mirena to market in the United States (Liletta®) with the goal of ensuring a lower price in the U.S. public sector market and providing LNG-IUS access in the developing world. This same product is comarketed around the world by various companies with names including Levosert® and Avibela®.
Types of IUDs
As we consider the variety of IUDs used over time, it is worth considering two characteristics: shape and component materials. IUDs have been developed in dozens of shapes and variations including rings, coils, Ts, and many other configurations (Figure 6.1). Currently, most common forms use a T shape. The two most common T forms are the Tatum-T whose arms are bent toward the stem to load into the inserter (like a person standing
with the hands in the front pockets) and the Nova-T whose arms are placed above the stem in the inserter (like a diver with arms above the head). Device component materials can be divided into the following groups: inert, copper, and hormone.
with the hands in the front pockets) and the Nova-T whose arms are placed above the stem in the inserter (like a diver with arms above the head). Device component materials can be divided into the following groups: inert, copper, and hormone.
 Figure 6.1 Selected IUDs available throughout the world. |
Inert Devices
Inert IUDs generate a local inflammatory reaction. Globally, women used inert steel and plastic IUDs in a range of shapes and sizes for contraception. The Lippes Loop was one popular inert IUD made of polyethylene impregnated with barium sulfate for radiographic identification. Removal of the Dalkon Shield from the U.S. market and data supporting greater efficacy for
medicated (e.g., copper and levonorgestrel-containing) devices gradually and completely replaced inert IUDs.
medicated (e.g., copper and levonorgestrel-containing) devices gradually and completely replaced inert IUDs.
Copper Devices
Since the 1980s, women’s health care providers in the United States have had access to only one copper IUD, the T380A (Paragard). The name emphasizes the components: T is the T shape, 380 is the amount of exposed surface area of copper on the polyethylene frame (380 mm2), and the A stresses the importance of the copper bands on the arms. The bands are why this design has a longer duration of action compared to other available copper IUDs with just copper wire wrapped tightly around the stem. The Food and Drug Administration (FDA) approved the T380A for 10 years although efficacy has been demonstrated up to 12 years17 and in a limited population up to 20 years.18
Over the last three decades, the U.S. market offered one copper IUD from one company. During this same time period, with greater competition and fewer barriers to regulatory approval, the European market provided over 30 different copper IUDs from several companies. These include different shaped devices with different copper quantities. In Europe, copper IUDs are considered devices and not drugs and must only demonstrate safety and not efficacy for approval.
Other TCu380 devices are also available. The TCu380Ag, approved in Finland, is identical to the TCu380A except that the copper wire on the stem has a silver core to prevent fragmentation and extend the lifespan of the copper. The TCu380 Slimline, approved in Canada and the United Kingdom, has tapered copper sleeves flush at the ends of the horizontal arms to facilitate easier loading and insertion. The performance of the TCu380Ag and the TCu380 Slimline is equal to that of the TCu380A.19,20 Other copperladen devices used worldwide include the TCu220C, the Nova-T, the Multiload-375, and the Sof-T. The TCu220C has a lower copper load on the Tatum-T frame. The Multiload-375 uses a unique frame that has 375 mm2 of copper wire wound around its stem. Product developers proposed that the flexible arms with multiple projections to contact the endometrium would minimize expulsions. This is a popular device in many parts of the world though it has similar efficacy and performance compared to the TCu380A.21 The copper Nova-T uses the same 32 × 32-mm frame as does the LNG-IUS, with 380 mm2 of copper on the stem only. The Mona Lisa® NT Mini IUD, currently approved in Europe and Canada, uses a smaller (22 × 30 mm) Nova-T frame permitting use of a narrower insertion tube, which could ease placement in some women; this system also wraps 380 mm2 of copper on the stem only. This device is being compared to the TCu380A in a U.S. randomized controlled trial (ClinicalTrials.gov NCT03124160).
A frameless IUD, the GyneFix® (also known as the Cu-Fix or the FlexiGard) consists of six copper sleeves (330 mm2 of copper) strung on a surgical nylon (polypropylene) thread that is knotted at one end. Lacking cross-arms, they minimally distort the uterine cavity. The knot is pushed into the myometrium during insertion with a notched needle that works
like a miniature harpoon. GyneFix is available in Mexico, Mongolia, Vietnam, Bolivia, Europe, China, Kenya, and Indonesia. Research demonstrated comparable efficacy to the TCu380A IUD over 8 years though more insertion failures, expulsions, and pregnancies in the first year of use.22,23
like a miniature harpoon. GyneFix is available in Mexico, Mongolia, Vietnam, Bolivia, Europe, China, Kenya, and Indonesia. Research demonstrated comparable efficacy to the TCu380A IUD over 8 years though more insertion failures, expulsions, and pregnancies in the first year of use.22,23
A novel approach to address the increased menstrual pain and bleeding frequently occurring with the TCu380A IUD is the addition of indomethacin in five different Chinese copper IUDs.24,25 Models of note include the Medicated Gamma Cu380, the Medicated Gamma Cu200, and the Active-γ-IUD. Chinese data demonstrate reduced bleeding and comparable efficacy of these devices when compared to other copper IUDs.24
The VeraCept IUD (Sebela Pharmaceuticals, Inc.) is a novel copper IUD on a flexible nickel and titanium alloy frame thought to better accommodate the uterine contour. The insertion tube diameter is narrower than the TCu380A, and the 175 mm2 of copper surface area, less than half of the TCu380A, is located just inside the cervical os and bilaterally at the tubal ostia. A randomized control trial (RCT) comparing VeraCept and TCu380A IUD users reported less insertion discomfort, fewer expulsions, and fewer pain or bleeding removals than copper T380A users.26 A U.S. phase 3 FDA study of this device is under way (ClinicalTrials.gov NCT03633799).
The Hormone-Releasing Intrauterine Systems (IUS)
Hormonal IUDs were developed in the 1970s in Chicago based on the discovery that administering progesterone inside the uterus could have contraceptive benefits. A Finnish doctor, Tapani Luukkainen, created the Progestasert IUS in 1976, which had a 1-year lifespan and never achieved widespread popularity. Sales of the Progestasert were discontinued in 1988.
The use of LNG in a capsule on an IUS stem provides extremely effective and safe contraception while reliably decreasing or eliminating menstrual bleeding. The first LNG-IUS, Mirena, was approved in 1991 in Europe and 2000 in the United States. This T-shaped device has a steroid-releasing reservoir covered by a rate-limiting membrane attached to the vertical stem, which contains LNG 52 mg dispersed in a polydimethylsiloxane capsule. It releases initially at a rate of 20 µg/d in vivo, progressively declining (reaching half of the initial rate after 5 years).27,28 The European Medicines Agency approved Levosert, another LNG 52 mg IUS made of similar components with reproducible clinical effects, in 2012. In 2015, the U.S. FDA approved its use with the product name Liletta. The FDA currently approves Mirena and Liletta for 5 years, but consistent evidence demonstrates contraceptive efficacy for at least 7 years.29,30 Manufacturers of both of these LNG-IUS systems have clinical trials in progress seeking to extend the approved duration of use for contraception beyond 5 years, with the Medicines360 study planned for 10 years (ClinicalTrials.gov NCT00995150, NCT02985541).
The LNG-IUS has multiple noncontraceptive benefits. Among these benefits is the ability of the LNG 52 mg IUS to treat heavy menstrual bleeding (HMB), endometrial hyperplasia, and dysmenorrhea. Treatment
of HMB is an approved indication throughout the world for Mirena and in every country outside the United States for Liletta31,32; a HMB trial for Liletta to have this approval in the United States is currently under way (ClinicalTrials.gov NCT03642210). The LNG 52 mg IUS is about as effective as endometrial ablation for HMB treatment.33,34,35 The high local levels of LNG at the endometrium provide strong suppression of proliferation useful for a variety of gynecologic conditions, and the literature supports off-label use for endometrial protection in women using tamoxifen, for postmenopausal women receiving estrogen therapy, for treatment of endometrial hyperplasia, and for dysmenorrhea.36,37,38,39,40,41,42,43
of HMB is an approved indication throughout the world for Mirena and in every country outside the United States for Liletta31,32; a HMB trial for Liletta to have this approval in the United States is currently under way (ClinicalTrials.gov NCT03642210). The LNG 52 mg IUS is about as effective as endometrial ablation for HMB treatment.33,34,35 The high local levels of LNG at the endometrium provide strong suppression of proliferation useful for a variety of gynecologic conditions, and the literature supports off-label use for endometrial protection in women using tamoxifen, for postmenopausal women receiving estrogen therapy, for treatment of endometrial hyperplasia, and for dysmenorrhea.36,37,38,39,40,41,42,43
Two lower-dose LNG-IUSs are also available. Both have narrower diameter insertion tubes (1 mm narrower) which may facilitate insertion for nulliparous women and cause less initial discomfort with insertion compared to LNG 52 mg IUSs.44 The FDA approved the LNG 13.5 mg IUS (Skyla) in 2013, which releases 14 µg/d after 24 days and declines to 5 µg/d after 3 years.45 The FDA approved the LNG 19.5 mg IUS (Kyleena) in 2016. This product releases 17.5 µg/d after 24 days and declines to 7.4 µg/d after 5 years.45 These lower-dose LNG-IUSs provide lower LNG serum concentrations, lower rates of anovulation, and less amenorrhea at 1 and 3 years compared to LNG 52 mg IUSs (Table 6.2).45 This may be a benefit for women who desire less bleeding but do not desire amenorrhea; however, users need to be aware that the bleeding is infrequently regular and clinical trials demonstrate discontinuation for bleeding complaints around 5% over 3 years of use for both lower-dose products (compared to 2% for the LNG 52 mg IUS).51,53 The reduction in insertion discomfort with the lower-dose devices should be weighed against less of a decline in bleeding and amenorrhea without a reduction in cost.44,51 It is worth noting that the FDA phase 3 ACCESS IUS study for the Liletta 52 mg IUS included 1,011 nulliparous women, 57.7% of participants. The trial demonstrated high efficacy, safety, and continuation among nulliparous women supporting that almost all women are candidates for the larger device.53 The LNG 52 mg IUS is further distinguished from
lower-dose LNG IUSs as it is approved for treatment of HMB and endometrial protection during hormone replacement therapy in many countries (but not the United States). Though we lack comparative studies, the higher local and systemic levels with the 52 mg IUS appear a more sensible choice than lower-dose IUSs for hyperestrogenic situations such as treatment of endometrial hyperplasia, treatment of HMB, and pelvic pain. Still, many women of all ages have concerns about hormonal dose, and counseling for IUD choice should include the pros and cons of the lower-dose systems. While not an approved option for HMB, the lower-dose LNG-IUS offers an alternative to a copper IUD in women with concerning menstrual bleeding or pain histories who would prefer to minimize hormonal dose.
lower-dose LNG IUSs as it is approved for treatment of HMB and endometrial protection during hormone replacement therapy in many countries (but not the United States). Though we lack comparative studies, the higher local and systemic levels with the 52 mg IUS appear a more sensible choice than lower-dose IUSs for hyperestrogenic situations such as treatment of endometrial hyperplasia, treatment of HMB, and pelvic pain. Still, many women of all ages have concerns about hormonal dose, and counseling for IUD choice should include the pros and cons of the lower-dose systems. While not an approved option for HMB, the lower-dose LNG-IUS offers an alternative to a copper IUD in women with concerning menstrual bleeding or pain histories who would prefer to minimize hormonal dose.
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Several companies produce and investigate LNG-IUSs that do not use the Nova-T frame. Available in Europe but not the United States are the 5-year Femilis® LNG 60 mg IUS with a cross-arm width of 28 mm and the 3-year Femilis 40 mg Slim with a width of 24 mm.24,54 Both of these systems use a novel frame with a solid flexible upper arm design that permits “pushin technique” of the inserter.55 Developers of the GyneFix and VeraCept copper IUDs are also applying their unique frame designs and inserters to LNG-containing IUSs. The frameless LNG device, called Fibroplant, continues development, and LevoCept, an LNG 52 mg IUS that uses the modified VeraCept (with a minimally wider inserter to accommodate the LNG capsule) has completed a phase 2 study (ClinicalTrials.gov NCT02882191).
IUD Evidence Versus Myths
Over time, conventional wisdom of appropriate IUD usage and practice has changed dramatically. Although the myths below no longer seem relevant given the high acceptance of intrauterine contraception, these misconceptions remain in the literature and the minds of some clinicians and women. Very strong evidence now exists to assure the safety of the listed practices. Specific rebuttals to each myth listed below follow in this chapter. We hope this information will lay to rest specific myths associated with IUDs. For reference, the following list includes evidence-based statements addressing some (outdated) common misconceptions among clinicians:
Mechanism of Action
Clinicians require a firm understanding of IUD mechanisms of action to inform potential users and avoid misconceptions, which limit access. Like many drugs, the precise mechanism of action of IUDs is not completely understood. However, strong clinical evidence in aggregate informs us that the timing of IUD effect is almost entirely prefertilization, by preventing sperm-egg union (e.g., contraception). No scientific human data support a postimplantation effect. The American College of Obstetricians and Gynecologists (ACOG) agrees with the biologic definition that pregnancy begins with the implantation of a fertilized egg.94 As such, IUDs are not abortifacients.56,57,58 However, it is unclear if in exceptional situations IUD alterations of the endometrium prevent a fertilized egg from implanting.95 The correct term for inhibition of implantation is contragestion (contragestation) and not abortion. Here, we review the objective scientific data explaining critical components of IUD action. The high efficacy of modern IUDs suggests multiple mechanisms at play, and these may vary by several factors including IUD type and time that the IUD is in place relative to last act of intercourse. For the interested reader, we recommend Ortiz and Croxatto’s rigorous review of the objective data on this subject.57
All IUD types create inflammatory, spermicidal environments in the endometrial cavity that prevent fertilization.57,96 Inert IUDs significantly increase the number of inflammatory cells in the uterine cavity, which release cytotoxic substances. The increased protein content in the endometrium of inert IUD users reflects cellular degradation from neutrophils and macrophages. These inflammatory cells have been shown to phagocytize sperm.97 While these inflammatory cells may also create a hostile uterine environment to negatively affect implantation, we lack direct evidence of this effect. High failure rates with inert devices likely occur due to more fertilizations. This led to the development of medicated IUDs.
The addition of copper to IUDs provides a release of free copper and copper salts that have spermicidal effect. Copper also has both a biochemical and morphologic impact on the endometrium and cervix producing alterations in cervical mucus and endometrial secretions. These include a sterile inflammatory response, marked by production in the endometrium of cytokine peptides known to be cytotoxic to sperm and inhibition of various endometrial enzymes.98 Direct evidence from detailed clinical experiments has shown that very few, if any, sperm reach the ovum in the fallopian tube. In women using copper IUDs, sensitive assays for human chorionic gonadotropin do not find evidence of fertilization.99,100 This is consistent with the fact that the copper IUD protects against both intrauterine and ectopic pregnancies.
The LNG-IUSs add the endometrial action of the progestin to the foreign body reaction. This hormonal action leads to endometrial decidualization, deceased response to estrogen through down-regulation of progesterone receptors, and atrophy of the glands causing a predictable decrease in bleeding frequency and intensity. We do not have evidence that these endometrial
changes provide a primary contraceptive effect.101 The available data strongly support prevention of fertilization via thickened mucus as the primary mechanism of action in LNG-IUS users. The high local release of LNG leads to the development of a progestin-mediated thickening of cervical mucus. This was demonstrated by light microscopy of cervical mucus, which showed a barrier to sperm penetration in LNG-IUS users compared to nonhormonal users (Figure 6.2).102 The high efficacy of the LNG-IUS in preventing pregnancy is incontrovertible. This is most likely due to lack of sperm penetration through highly unfavorable cervical mucus. Limitations of the certainty of this statement come from the lack of scientific data demonstrating the quantity, motility, and function of sperm with LNG-IUS use. However, high levels of local LNG may have deleterious effects on spermegg interaction through interference with sperm transport, capacitation, and the acrosome reaction.103 In addition, LNG delivered from the IUD may impair oviduct transport via an effect on tubal motility.104,105,106 Efficacy may also be augmented by modest decreases in ovulatory function during early use of the LNG-IUS. After the first year, cycles are ovulatory in 50% to 75% of women, regardless of their bleeding patterns.107
changes provide a primary contraceptive effect.101 The available data strongly support prevention of fertilization via thickened mucus as the primary mechanism of action in LNG-IUS users. The high local release of LNG leads to the development of a progestin-mediated thickening of cervical mucus. This was demonstrated by light microscopy of cervical mucus, which showed a barrier to sperm penetration in LNG-IUS users compared to nonhormonal users (Figure 6.2).102 The high efficacy of the LNG-IUS in preventing pregnancy is incontrovertible. This is most likely due to lack of sperm penetration through highly unfavorable cervical mucus. Limitations of the certainty of this statement come from the lack of scientific data demonstrating the quantity, motility, and function of sperm with LNG-IUS use. However, high levels of local LNG may have deleterious effects on spermegg interaction through interference with sperm transport, capacitation, and the acrosome reaction.103 In addition, LNG delivered from the IUD may impair oviduct transport via an effect on tubal motility.104,105,106 Efficacy may also be augmented by modest decreases in ovulatory function during early use of the LNG-IUS. After the first year, cycles are ovulatory in 50% to 75% of women, regardless of their bleeding patterns.107
Several studies have flushed the uterine cavity through the cervix or an excised portion of the fallopian tube at the time of surgery to assess for the presence of sperm and fertilized ova. The most robust clinical data come from a 1988 prospective assessment by Alvarez et al. In this study, researchers flushed the uterus and fallopian tubes of two groups of women undergoing
salpingectomy within 132 hours of the LH peak. The experimental group included 56 women with a variety of inert, copper and hormonal IUDs. Their tubal flushings were compared to 115 women using no contraception. The tubal flushings returned eggs from 39% of IUD users and 56% of control participants. The uterine flushing returned no eggs from IUD users and 4 from the 115 control subjects. A subset of participants with retrieved eggs reported intercourse from 70 hours before to 11 hours after the LH peak and had evidence of spermatozoa in their cervical mucus. None of the 14 IUD users had eggs with evidence of fertilization versus 10 of 20 control participants whose eggs showed 2- to 8-cell postfertilization development.108
salpingectomy within 132 hours of the LH peak. The experimental group included 56 women with a variety of inert, copper and hormonal IUDs. Their tubal flushings were compared to 115 women using no contraception. The tubal flushings returned eggs from 39% of IUD users and 56% of control participants. The uterine flushing returned no eggs from IUD users and 4 from the 115 control subjects. A subset of participants with retrieved eggs reported intercourse from 70 hours before to 11 hours after the LH peak and had evidence of spermatozoa in their cervical mucus. None of the 14 IUD users had eggs with evidence of fertilization versus 10 of 20 control participants whose eggs showed 2- to 8-cell postfertilization development.108
 Figure 6.2 Effect of intrauterine delivery of levonorgestrel on cervical mucus. In vitro sperm penetration through cervical mucus obtained at midcycle from women using a LNG 52 mg IUS (left panel) and from controls using no hormonal method (right panel). The thick wall of mucus created in response to the presence of the LNG-IUS demonstrates its primary mechanism of action. Sperm (small white dots) is present throughout the control sample and absent from the thick mucus produced in users of the LNG-IUS. (Reprinted from Lewis RA, Taylor D, Natavio MF, Melamed A, Felix J, Mishell D Jr, Effects of the levonorgestrel-releasingintrauterine system on cervical mucus quality and sperm penetrability, Contraception 82(6):491-496, 2010. Copyright © 2010 Elsevier. With permission.) |
The accumulation of data demonstrates that sperm transport to the potential site of fertilization is severely compromised in IUD users. The lack of sperm and egg interaction explains the vast majority of IUD efficacy. Although pregnancies uncommonly occur in IUD users, the methods are not 100% effective. This provides strong evidence against a hostile endometrial environment that prevents implantation as a primary mechanism for the contraceptive effect. Our best evidence supports that in general use, an IUD functions as a contraceptive and prevents fertilization. When this primary mechanism fails, the fertilized egg has the opportunity to implant in the fallopian tube or uterine cavity, or fail to implant. While the presence of an IUD may reduce the potential of a fertilized egg to successfully implant, we lack direct experimental evidence of this effect.
Emergency Contraception
Under typical use, IUDs prevent fertilization and have a contraceptive mechanism of action. However, copper IUDs appear to have a contragestive effect when placed during the preimplantation window. This allows use of a copper IUD for emergency contraception up to 5 days after ovulation following unprotected intercourse. High levels of copper, present due to burst release following copper IUD placement, likely contribute to this enhanced effect.109 The fact that copper IUDs function well for emergency contraception does not support an effect on implantation as a primary mechanism of action during regular contraception. We have no evidence for use of the LNG-IUS for emergency contraception. (see discussion of clinical use of IUDs for emergency contraception on page 201).
Noncontraceptive Benefits of the IUD
The LNG-IUS and the copper IUD both provide many noncontraceptive benefits (Box 6.1). The LNG 52 mg IUS is an effective treatment for heavy uterine and abnormal uterine bleeding (AUB). Through down-regulation of endometrial estrogen receptors, the endometrium becomes inactive with decreased proliferation and bleeding. The effect of local LNG is more effective than the administration of oral progestins, combined hormonal contraceptives, or inhibitors of prostaglandin synthesis and compares favorably with surgical treatment (hysterectomy or endometrial ablation).33,110,111,112,113,114,115,116,117,118,119
Box 6.1 Summary of Noncontraceptive Benefits of the IUD (Approved Indications in the United States Noted Where Applicable)
Reduction of heavy menstrual bleeding (FDA approved for Mirena), abnormal uterine bleeding, and improvement of related anemia (LNG 52 mg)33,72,73,74,75,76,77,78,79,80,81,82,83,84,85
Reduction of menstrual bleeding in women with hemostatic disorders and in anticoagulated women (LNG 52 mg)87,88,89,90,91,92,93
Treatment of primary dysmenorrhea (LNG 52 mg)116
Reduction of myoma prevalence as well as uterine volume and bleeding associated with myomas (LNG 52 mg)94,98,99,100,101
Treatment of endometriosis and pain associated with endometriosis (LNG 52 mg)52,53,117,118,119,120,121,122,123,124
Decrease in uterine volume and pain associated with adenomyosis (LNG 52 mg)115
Protection against polyps associated with postmenopausal estrogen therapy or tamoxifen treatment (LNG 52 mg)36,38,39,40,41,42,117,118,119
Conservative treatment of endometrial hyperplasia or low-risk endometrial cancer (LNG 52 mg)52,120,121,122,123,124,129
Initial clinical observations that users of the LNG 52 mg IUS for contraception experienced high rates of discontinuation for amenorrhea led to clinical studies designed to evaluate this as a health benefit and improve counseling regarding expected bleeding patterns. The LNG 52 mg IUS rapidly decreases dysmenorrhea and menstrual blood loss (about 40% to 50%). Bleeding over time can be reduced by 90%, with 1 in 5 women becoming amenorrheic 1 year after insertion (actually this rate is achieved by 9 months) and 1 in 3 by 3 years (Table 6.2).120,121,122,138 Amenorrhea rates remain around 40% through 5 years of use.123 Average long-term hemoglobin and iron levels increase compared with preinsertion values.123 The LNG 19.5 mg IUS and LNG 13.5 mg IUS result in lower rates of amenorrhea at 1 and 3 years (Table 6.2).139 Bleeding patterns for all LNG-IUSs improve over time with decreases in the number of spotting and bleeding days.51,52
Additionally, the LNG 52 mg IUS can be safely and effectively used in women with inherited bleeding disorders and in women using anticoagulation therapy to reduce heavy bleeding. In small retrospective studies, women with inherited bleeding disorders (von Willebrand’s disease being the most common) saw a significant decrease in the amount of bleeding and an amenorrhea rate of 56% at 9 months.124 In a study of women on warfarin therapy, 87% experienced a reduction in menstrual blood loss with the
LNG-IUS.129 However, these women may require earlier replacement (e.g., before 5 years) of the LNG-IUS if heavy bleeding returns.124,125,126,127,129,140,141
LNG-IUS.129 However, these women may require earlier replacement (e.g., before 5 years) of the LNG-IUS if heavy bleeding returns.124,125,126,127,129,140,141
The LNG 52 mg IUS also reduces bleeding in the presence of leiomyomas.128,142,143,144,145 Limited evidence supports that the LNG-IUS reduces the prevalence of leiomyomas and decreases uterine volume.19,128,142,143,146 The presence of uterine leiomyomas may also lead to higher IUD expulsion rates. However, use of the LNG-IUS should be considered in women with fibroids due to the benefit of achieving reduced blood flow in up to 90% and amenorrhea in up to 44.5%.143,147,148 The presence of a submucosal leiomyoma is a relative contraindication to use of the LNG-IUS, as these women may not respond favorably to treatment and placement may be more difficult.149
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