A small device, five different clocks

An intrauterine device is a T-shaped contraceptive placed in the uterus by a trained clinician. The CDC groups them as levonorgestrel IUDs, which release a progestin, and the copper T. On the CDC's August 2024 method page, typical-use failure is 0.1% to 0.4% for levonorgestrel IUDs and 0.8% for the copper T. Those are pregnancies in the first year per 100 users, counting ordinary use. The 2024 U.S. Selected Practice Recommendations put it in one line: fewer than one IUD user out of 100 becomes pregnant in the first year. The same guidance says IUDs can be used by adolescents and by people who have and have not given birth. They do not protect against sexually transmitted infections. A condom still does that job.

How long a device may stay in depends on the brand, not on the word "IUD."

Levonorgestrel devices, from the labels and MedlinePlus

Mirena contains 52 mg of levonorgestrel. The FDA label says it prevents pregnancy for up to 8 years and should be replaced after the eighth year. It is also approved to treat heavy menstrual bleeding for up to 5 years in people who want an IUD for contraception. If bleeding treatment is still needed after five years, the label says to replace it, because data past five years for that use are limited. The release rate is about 21 micrograms a day after 24 days, falling to about 11 micrograms a day after 5 years and about 7 after 8 years.

The label is frank about mechanism. The local way continuously released levonorgestrel prevents pregnancy "has not been conclusively demonstrated." Studies suggest thickening of cervical mucus so sperm have trouble passing, inhibition of sperm capacitation or survival, and a change in the endometrium. Ovulation is not reliably stopped. In one 1-year study, about 45% of cycles were ovulatory. In another study after 4 years, 75% of cycles were ovulatory. So a hormonal IUD is not "turning the ovaries off" in most cycles later on.

Mirena is contraindicated as emergency contraception. The label says it cannot be used for post-coital contraception. Do not ask a clinic to insert Mirena as a morning-after device.

Liletta is also a 52 mg levonorgestrel system. MedlinePlus states it may be left in place for up to 8 years for pregnancy prevention, and for up to 5 years when it is being used to treat heavy menstrual bleeding.

Kyleena contains 19.5 mg and is approved for up to 5 years. The label describes a release of about 17.5 micrograms a day after 24 days, declining to about 7.4 micrograms a day after 5 years. Blue removal threads and a silver ring visible on ultrasound distinguish it from other devices.

Skyla contains 13.5 mg. MedlinePlus says it may be left in place for up to 3 years.

CDC's public summary matches this spread: a levonorgestrel IUD stays in for up to 3 to 8 years, depending on the device.

The copper IUD

Paragard is a polyethylene T with copper wire and copper collars. The 2019 FDA label describes a total exposed copper surface of 380 ± 23 square millimeters and an indication for pregnancy prevention for up to 10 years. Remove it no later than 10 years from insertion. The label says to examine the patient after her first period to confirm it is still in place.

Copper released into the uterus contributes to the effect. The label's mechanisms are interference with sperm transport and fertilization, and possibly prevention of implantation. There is no hormone and no estrogen-related clot discussion of the kind that applies to combined pills.

The CDC says a copper IUD can be inserted within 5 days of unprotected sex as emergency contraception. That use is specific to the copper device. It is not a license to use a hormonal IUD the same way. Mirena's label forbids that use.

Paragard is contraindicated in Wilson's disease and in anyone with hypersensitivity to copper or to trace elements in the copper. Heavier periods and cramping are among the adverse reactions listed in clinical-trial reporting on the label, along with backache, pain with sex, spotting, and expulsion.

Who should not have one inserted

Labels are the authority here, and they are not identical.

Shared problems include known or suspected pregnancy, a uterus distorted by fibroids or another anomaly, current pelvic inflammatory disease, postpartum or post-abortion endometritis in the past 3 months, known or suspected uterine or cervical cancer, bleeding from the uterus with no known cause, untreated cervicitis or vaginitis or another lower-genital infection, conditions that raise susceptibility to pelvic infection, and an IUD that is already in place and has not been removed.

Mirena adds a history of PID unless there has been a pregnancy in the uterus since, known or suspected breast cancer or another progestin-sensitive cancer now or in the past, acute liver disease or a liver tumor, and use as emergency contraception. Untreated bacterial vaginosis is specifically named among infections that should be controlled before Mirena goes in.

Paragard adds Wilson's disease and copper allergy, and does not carry the breast-cancer or liver-tumor contraindications that come with a progestin.

CDC practice guidance still allows IUDs for adolescents and for people who have never given birth, when none of these contraindications apply. "I have not had a baby" is not, by itself, a reason the CDC withholds an IUD.

Insertion, strings, and the first weeks

Insertion is an in-office procedure by someone trained to do it. The clinician rules out pregnancy, checks that the uterus is a suitable size and shape, and places the device at the fundus. The Mirena label says a uterus that sounds to less than 6 cm may raise the chance of expulsion, bleeding, pain, perforation, and pregnancy. If Mirena is not inserted in the first seven days of the menstrual cycle, use a barrier method or avoid vaginal sex for seven days, unless it was placed right after a first-trimester abortion. The label says to cut the threads so about 3 cm remain visible outside the cervix, and not to pull on them while cutting.

Pain varies. The label's instruction to the clinician is to prescribe an analgesic if indicated, and to investigate exceptional pain or bleeding during or after insertion immediately, including with ultrasound, to exclude perforation. Ask what pain plan that clinic actually offers. Do not assume a blog's ibuprofen dose is the one they want you to take.

Check that you can feel the threads, or have the clinician confirm placement, especially after the first period with a copper IUD, which is what the Paragard label asks for. You should not feel the plastic of the device itself. A partner sometimes feels threads. Threads can be trimmed. If you cannot feel threads that you could feel before, or you feel the hard end of the device, call. Threads can curl up into the cervix, and they can also signal expulsion.

Expulsion, perforation, and pregnancy with an IUD in place

Partial or complete expulsion may be silent and then the contraceptive effect is gone. In Mirena clinical trials, a 4.5% expulsion rate was reported over the 5-year study. Risk is higher when insertion is immediately after delivery. An increase in bleeding can be a clue. A partially expelled device is removed. A new one can be placed when the clinician is sure that is appropriate.

Perforation, the device going into or through the uterine wall, usually happens at insertion and may be noticed later. The Mirena label says risk is higher in people who recently gave birth and in people who are breastfeeding at insertion. Surgery is sometimes required. Perforation can also mean the device no longer prevents pregnancy.

If pregnancy occurs with Mirena in place, the label says to evaluate for ectopic pregnancy, because about half of pregnancies with Mirena in place are ectopic. The rate of ectopic pregnancy in Mirena trials, which excluded people with a prior ectopic pregnancy, was about 0.1% per year. Prior ectopic pregnancy, tubal surgery, or pelvic infection raises concern. An intrauterine pregnancy with Mirena still inside also carries risk, including pregnancy loss and infection. The label says to remove the device because leaving it in may increase the chance of spontaneous abortion and other complications. That removal decision is urgent and individual.

With Paragard, a pregnancy that occurs is more likely to be ectopic than a pregnancy in the general population, and users still have a lower ectopic risk than sexually active people using no contraception at all. The trial incidence cited on the label was about 0.06%. Any pregnancy with an IUD in place needs same-day clinical care, especially with one-sided pain, shoulder pain, fainting, or bleeding.

Pelvic infection is most likely when organisms are introduced at insertion. The Paragard label tells patients to report abdominal or pelvic pain, odorous discharge, unexplained bleeding, fever, or genital sores. Recurrent or severe pelvic infection is a reason to remove the device. An IUD does not protect you from the STIs that cause many of those infections.

Removal and what comes next

A clinician removes an IUD by gentle traction on the threads. It can come out whenever you want a pregnancy or a different method. You do not have to wait for the approved year limit. If Mirena is removed and pregnancy is not desired, the label says to remove it during the first 7 days of a regular cycle, or to start another method a week before removal if the timing is different or periods are absent. Otherwise there is a pregnancy risk in that gap.

Choosing an IUD in the first place is easier beside the other typical-use numbers. Those are in How to Choose the Right Contraception Method.

The decision that actually belongs to you, before anyone opens a sterile package, is whether you want a hormone in the uterus, copper and possibly heavier periods, or a method you control yourself every day.

Sources

Educational only. Insertion, pain control, ectopic pregnancy, and removal are clinical care. Label years can change. Confirm the current FDA label for the exact device you are offered.