Intrauterine devices fall into two broad categories: copper IUDs, which use no hormones, and hormonal IUDs, which release a small dose of levonorgestrel (a progestin). Both sit inside the uterus, both rank among the most effective reversible contraceptives available, and both last for years. But the similarities end there. The two types work through different mechanisms, produce different bleeding patterns, carry different side-effect trade-offs, and suit different clinical situations in ways that matter when you’re choosing between them.
How Each Type Works
A copper IUD is a small, T-shaped plastic frame wound with copper wire. Once placed in the uterus, the copper continuously releases ions that trigger a local inflammatory response in the uterine lining. Those copper ions reach concentrations throughout the reproductive tract that are directly toxic to sperm, impairing their ability to move and survive. The effect extends beyond the uterus itself: the entire genital tract is affected, which reduces the chances of fertilization and makes it far less likely that any embryo could implant successfully.1PubMed. Copper-T intrauterine device and levonorgestrel intrauterine system: biological bases of their mechanism of action No hormones are involved at any step.
A hormonal IUD releases levonorgestrel locally into the uterus. The progestin thickens cervical mucus so sperm have difficulty passing through, thins the uterine lining so it becomes less hospitable to implantation, and in some users partially suppresses ovulation. Because the hormone acts mostly at the uterus and cervix rather than circulating at high levels through the bloodstream, systemic hormonal side effects tend to be milder than with oral contraceptives or implants.
Efficacy and How the Numbers Compare
Both IUD types are extremely effective. The copper T-380A, which is the most widely studied copper device, has a failure rate of less than one pregnancy per 100 users in the first year.2PubMed Central. Long-term safety, efficacy, and patient acceptability of the intrauterine Copper T-380A contraceptive device Hormonal IUDs are at least as effective, and a large European surveillance study found that the levonorgestrel IUD had a Pearl index of 0.06 compared with 0.52 for copper IUDs, meaning the hormonal device had roughly one-eighth the pregnancy rate.3PubMed. Comparative contraceptive effectiveness of levonorgestrel-releasing and copper intrauterine devices: the European Active Surveillance Study for Intrauterine Devices In practical terms, both types put you well under a one-in-a-hundred chance of pregnancy per year, which is comparable to sterilization.
The hormonal IUD’s edge in efficacy is real but small enough that it rarely drives the choice on its own. More often, the decision comes down to bleeding preferences, hormone tolerance, and whether you want non-contraceptive benefits.
Hormonal IUD Dose Tiers
Not all hormonal IUDs are the same device. In the U.S. and most of Europe, levonorgestrel IUDs are available in several dose tiers. The highest-dose version (52 mg total levonorgestrel) is approved for up to eight years and delivers the strongest effect on the uterine lining. Lower-dose options (19.5 mg and 13.5 mg) are physically smaller, which can make insertion easier in people with a smaller uterus, but they are approved for shorter durations (typically five and three years, respectively). They also thin the lining less aggressively, so your chance of losing your period entirely is lower with the smaller devices.
These dose differences matter beyond just contraception. When researchers looked at ectopic pregnancy rates across IUD types, the 52-mg levonorgestrel device was associated with a lower ectopic pregnancy rate than the copper IUD, while the 13.5-mg device actually had a higher rate. At one year, ectopic pregnancy occurred at a rate of about 0.04 per 100 person-years with the 52-mg device and 0.07 with the copper IUD, while the 13.5-mg device showed a rate of 0.18.4PubMed. Intrauterine Devices and Risk of Ectopic Pregnancy This likely reflects the stronger ovulation suppression at the higher dose. To be clear, ectopic pregnancy is rare with any IUD, but if you have risk factors for ectopic pregnancy, this distinction between dose tiers is worth discussing with your clinician.
Bleeding Patterns and How They Diverge Over Time
This is probably the biggest day-to-day difference between the two types, and the pattern changes substantially over the first year. In a study tracking users of both devices over twelve months, the early months looked like this: at three months, about 40% of hormonal IUD users reported irregular spotting, compared with about 16% of copper IUD users. But heavy bleeding went the other direction: roughly 42% of copper IUD users experienced heavy periods at three months, versus about 10% of hormonal users.5International Journal of Drug Delivery Technology. Comparative bleeding patterns in users of hormonal IUD vs. copper IUD over 12 months
By twelve months, the hormonal IUD’s pattern resolved in a striking way: roughly 44% of hormonal IUD users had stopped menstruating entirely, while none of the copper IUD users had. Heavy bleeding persisted in about 23% of copper users versus under 5% of hormonal users.6International Journal of Drug Delivery Technology. Comparative bleeding patterns in users of hormonal IUD vs. copper IUD over 12 months A meta-analysis confirmed the broader picture: hormonal IUDs carried roughly three and a half times the risk of amenorrhea (no periods) and about three times the risk of very light periods compared to copper, but copper users were about two and a half times as likely to experience increased bleeding and heavy periods.7The Lancet Regional Health. Efficacy and safety of copper intrauterine devices versus levonorgestrel-releasing intrauterine devices: a systematic review and meta-analysis
The same meta-analysis found that hormonal IUDs roughly halved the risk of painful periods compared with copper IUDs. If you already have heavy or painful periods, this pattern has obvious implications for which type will feel better over the long term.
The Copper IUD as Emergency Contraception
One role that belongs exclusively to the copper IUD is emergency contraception. Inserted within five days of unprotected sex, the copper IUD is the most effective emergency contraceptive available. In one study, no pregnancies occurred among 318 people who received a copper IUD for emergency contraception, preventing all expected pregnancies.8PubMed Central. Estimating emergency contraception efficacy with levonorgestrel and copper intrauterine devices A systematic review comparing the copper IUD to oral emergency contraception found a failure rate of about 0.1% for the copper IUD versus about 1.5% for oral methods.9PubMed. The intrauterine device versus oral hormonal methods as emergency contraceptives: A systematic review of recent comparative studies
The same study on emergency use found that the 52-mg levonorgestrel IUD also performed well, preventing around 93 to 96% of expected pregnancies.10PubMed Central. Estimating emergency contraception efficacy with levonorgestrel and copper intrauterine devices This is a relatively newer finding and guidelines on hormonal IUD use for emergency contraception are still evolving in many countries, but it suggests the copper IUD is no longer the only IUD option in an urgent situation. The copper device remains the better-established choice, with its 100% prevention rate in the available data.
Non-Contraceptive Uses of the Hormonal IUD
The levonorgestrel IUD has become a treatment in its own right for several gynecological conditions, separate from its role in preventing pregnancy. Heavy menstrual bleeding is the most common non-contraceptive indication. In one study, people with heavy periods who used a hormonal IUD for six months saw their menstrual assessment scores climb from about 52% to 84%, with significant drops in depression scores as well.11PubMed Central. Levonorgestrel-releasing intrauterine device treatment in heavy menstrual bleeding: Correlation with endometrial pathology and quality of life The improvements in bleeding control held regardless of whether biopsy showed underlying endometrial pathology.
Adenomyosis, a condition where tissue from the uterine lining grows into the muscular wall of the uterus and causes pain and heavy bleeding, also responds to the hormonal IUD. A three-year study found that pain scores and bleeding scores dropped significantly in all subtypes of adenomyosis after IUD insertion, and by the end of the study none of the participants had scores indicating heavy menstrual blood loss.12PubMed Central. Efficacy of the levonorgestrel-releasing intrauterine device is associated with different subtypes of adenomyosis: a retrospective study
During the menopausal transition, the hormonal IUD can serve double duty. People on estrogen replacement therapy need a progestogen to protect the uterine lining from overgrowth. A review of randomized trials found that none of the participants using a levonorgestrel IUD alongside estrogen therapy developed endometrial hyperplasia, making it an effective alternative to oral or vaginal progesterone for endometrial protection.13PubMed Central. Benefits of Levonorgestrel Intrauterine Device Use vs. Oral or Transdermal Progesterone for Postmenopausal Women Using Estrogen Containing Hormone Therapy The copper IUD has no therapeutic uses beyond contraception and emergency contraception.
Expulsion and Perforation Risks
Both IUD types can be expelled (partially or completely pushed out by the uterus) or, rarely, perforate the uterine wall during or after insertion. A large cohort study found overall five-year expulsion rates of about 4.6%, with the rate lowest when insertion happened more than six weeks postpartum and highest when done within three days of delivery, where the five-year rate reached about 10.7%.14PubMed Central. Risks of Uterine Perforation and Expulsion Associated With Intrauterine Devices A meta-analysis of postpartum placement confirmed this gradient: immediate placement (within ten minutes of placental delivery) had a pooled expulsion rate of about 10%, early placement (up to four weeks) reached nearly 30%, and interval placement (four weeks or later) dropped to under 2%.15PubMed Central. Intrauterine Device Expulsion After Postpartum Placement: A Systematic Review and Meta-analysis
Heavy menstrual bleeding was the strongest risk factor for expulsion independent of timing, along with younger age (especially under 25), higher parity, and higher body weight.16PubMed Central. Demographic, Reproductive, and Medical Risk Factors for Intrauterine Device Expulsion
Uterine perforation is rarer. The large APEX-IUD study reported a five-year cumulative perforation incidence of about 0.29% among non-postpartum users. The risk was highest when insertion occurred between four days and six weeks postpartum, with about a seven-fold increase compared with non-postpartum insertion. Breastfeeding at the time of insertion also modestly increased the risk.17PubMed. Intrauterine device-related uterine perforation incidence and risk (APEX-IUD): a large multisite cohort study An updated systematic review confirmed that breastfeeding at the time of insertion is associated with a higher relative risk of perforation, with estimates ranging from about 1.4 to 10 times the risk, though the absolute rate remained low.18PubMed Central. The safety of intrauterine devices during breastfeeding: an updated systematic review
Infection Risk and STIs
An older generation of IUD fears centered on pelvic inflammatory disease, largely due to problems with a device from the 1970s that was pulled from the market. Modern IUDs carry a very low risk of PID.19PubMed Central. Intrauterine devices & infection: review of the literature The risk that does exist is concentrated in the first few weeks after insertion and is linked to pre-existing sexually transmitted infections rather than to the device itself. A systematic review found that people with chlamydia or gonorrhea at the time of insertion had a higher risk of PID, but the absolute risk was still low: zero to 5% for those with an STI at insertion and zero to 2% for those without.20PubMed. Does insertion and use of an intrauterine device increase the risk of pelvic inflammatory disease among women with sexually transmitted infection? A systematic review This is why many providers screen for STIs around the time of insertion but do not require results before placing the device, since delaying contraception also carries risk.
IUDs in Younger and Nulliparous Users
The idea that IUDs are only appropriate for people who have already given birth persists, but the evidence says otherwise. A comprehensive review concluded that IUDs are effective regardless of age and parity, and that expulsion rates among people who have never been pregnant are not elevated compared with older parous adults.21PubMed. Intrauterine device use is safe among nulligravidas and adolescent girls Adolescents do have higher expulsion rates and higher early removal rates, but the removals appear driven more by lower tolerance of bleeding and pain side effects than by a physical mismatch with the device.
For copper IUDs specifically, earlier research comparing parous and nulliparous users found that nulliparous users had somewhat higher rates of expulsion and removal for bleeding and pain, and that smaller IUD designs might perform better in this group.22PubMed. Copper intrauterine device use by nulliparous women: review of side effects The lower-dose, physically smaller hormonal IUDs were designed in part to address this: their narrower insertion tube and smaller frame make them easier to place in a uterus that has never been stretched by pregnancy.
Frameless Copper IUDs
Most copper and hormonal IUDs are “framed” devices, meaning they have a rigid or semi-rigid T-shaped body. The frame holds the device in place but can contribute to cramping and expulsion, especially in smaller uteri. A frameless copper IUD (marketed as GyneFix in some countries) takes a different approach: it consists of copper sleeves strung on a suture thread that is anchored into the muscular wall of the uterus, with no rigid frame at all.
An eight-year randomized trial comparing the frameless device to the standard T-380A found trade-offs in both directions. The frameless IUD had more insertion failures and more first-year expulsions and pregnancies. But from the second through the eighth year, it had fewer pregnancies, fewer ectopic pregnancies, and fewer removals for pain than the T-shaped device.23PubMed. The frameless copper IUD (GyneFix) and the TCu380A IUD: results of an 8-year multicenter randomized comparative trial The anchoring technique requires specific training, which limits availability. A review of fifteen years of clinical experience with frameless devices concluded that the design reduces side effects and discomfort compared with framed IUDs, but the technique-dependent insertion remains a barrier to wider adoption.24PubMed. The ‘frameless’ intrauterine system for long-term, reversible contraception: a review of 15 years of clinical experience
Managing Insertion Pain
Insertion discomfort is one of the most common reasons people hesitate to get an IUD. The procedure itself takes only a few minutes, but it involves passing the device through the cervix, which can cause sharp cramping. A network meta-analysis of pain-reduction strategies found that a topical lidocaine-prilocaine cream applied to the cervix ranked highest for reducing pain both at the moment the cervix is grasped and during actual device placement. Paracervical lidocaine injection ranked second.25PubMed. Evaluating different pain lowering medications during intrauterine device insertion: a systematic review and network meta-analysis Over-the-counter oral painkillers taken beforehand have not been shown to make much difference in most studies, despite being commonly recommended. If you are concerned about insertion pain, asking your provider about topical anesthetic or a paracervical block is a more evidence-based approach.
Return to Fertility After Removal
One advantage shared by both IUD types is that fertility returns quickly once the device is removed. A systematic review and meta-analysis found a pooled pregnancy rate of about 83% within twelve months of stopping contraception, and this rate was not significantly different between hormonal methods and IUD users.26PubMed Central. Return of fertility after discontinuation of contraception: a systematic review and meta-analysis An older randomized study comparing the levonorgestrel IUD directly to the copper T-380A found that one-year pregnancy rates exceeded 90% for both groups, with a median time to planned pregnancy of three to four months. Duration of IUD use did not affect the speed of return.27Contraception. Recovery of fertility after use of the Levonorgestrel 20 mcg/d or copper T 380 Ag intrauterine device
Ectopic Pregnancy and IUDs
There is a persistent misconception that IUDs cause ectopic pregnancies. In reality, because IUDs prevent pregnancy so effectively, the absolute number of ectopic pregnancies is lower among IUD users than among people using no contraception at all. A meta-analysis of case-control studies concluded that current IUD use does not increase the risk of ectopic pregnancy. What is true is that if an IUD fails and a pregnancy does occur with the device in place, that pregnancy is more likely to be ectopic than a pregnancy conceived without an IUD.28Contraception. IUD use and the risk of ectopic pregnancy: A meta-analysis of case-control studies The distinction matters: the IUD is not creating ectopic pregnancies, it is just preventing intrauterine pregnancies more effectively than it prevents the rarer ectopic ones.
Why People Keep or Remove Their IUDs
Continuation rates offer a practical measure of how livable an IUD is over time. A large retrospective study found four-year continuation rates of about 45% for levonorgestrel IUDs and about 33% for copper IUDs. Among hormonal IUD users who discontinued, the leading reason was device expiration (about a third), followed by wanting to become pregnant, then pain. Among copper IUD users, the top reasons were expulsion and changes in bleeding pattern.29PubMed Central. Continuation of copper and levonorgestrel intrauterine devices: a retrospective cohort study
Shorter-term data tell a similar story. At twelve months, a prospective study found continuation rates of 88% for the levonorgestrel IUD and 84% for the copper IUD. The most common reason for discontinuing either device was bleeding or cramping, but it drove far more copper removals: about 14% of all copper IUD users stopped for those reasons, versus about 5% of hormonal IUD users.30PubMed Central. Continuation and Satisfaction of Reversible Contraception A systematic review confirmed that discontinuation rates due to bleeding are consistently higher for copper IUDs than for hormonal ones.31PubMed Central. Discontinuation rates of intrauterine contraception due to unfavourable bleeding: a systematic review
These numbers highlight a real tension in choosing a copper IUD: it avoids hormones entirely, which some people strongly prefer, but it demands you tolerate heavier, sometimes more painful periods. For people whose baseline periods are already heavy, that trade-off is especially steep. Conversely, some people find the unpredictable spotting or loss of periods with a hormonal IUD psychologically uncomfortable, even if it is medically harmless. Neither reaction is irrational, and knowing about these patterns beforehand helps you set realistic expectations.
Postpartum Placement Timing
Getting an IUD placed right after delivery is convenient, since you are already in a clinical setting and the cervix is dilated. But the timing creates a trade-off with expulsion risk. Immediate postpartum placement (within ten minutes of delivering the placenta) carries an expulsion rate roughly seven to eight times higher than waiting until at least four weeks postpartum.32PubMed Central. Intrauterine Device Expulsion After Postpartum Placement: A Systematic Review and Meta-analysis Early placement (between ten minutes and four weeks) is associated with the highest expulsion rates of all, approaching 30% in the pooled data. Waiting six or more weeks brings the rate close to the baseline for non-postpartum insertion.
Despite the higher expulsion risk, immediate postpartum placement has a practical benefit: people who plan to return for later insertion often don’t. In settings where follow-up is uncertain, placing the device immediately and accepting the higher chance of expulsion can result in more net contraceptive coverage at the population level. If you know you will reliably attend a follow-up visit, waiting until about six weeks postpartum gives the device its best chance of staying in place. If follow-up is uncertain, immediate placement may still be the better gamble.
One additional consideration for postpartum insertion is the perforation risk during breastfeeding. The APEX-IUD study found that breastfeeding at the time of insertion modestly increased the risk of uterine perforation, though the absolute incidence remained low.33PubMed. Intrauterine device-related uterine perforation incidence and risk (APEX-IUD): a large multisite cohort study This does not mean breastfeeding people should avoid IUDs, but it is a factor providers consider when counseling on timing.