Mirena is a contraceptive hormonal intrauterine device (IUD) made by Bayer Healthcare. It is made of a medication-eluting plastic containing the contraceptive hormone, levonorgestrel which is released into the uterus for up to 5 years.

Quick Summary
Mirena IUD

Mirena is a hormonal intrauterine device (IUD) made by pharmaceutical giant, Bayer Healthcare which was approved in 2000 in the U.S. and is said to be 99% effective at preventing pregnancy. Mirena IUD is implanted in the uterus and left in place for up to five years and is constructed of a medication-eluting plastic, which releases the contraceptive hormone levonorgestrel over a period of up to 5 years.

Mirena Side Effects

Because Mirena releases levonorgestrel into the uterus rather than into the bloodstream, a smaller amount of the hormone is used than other methods.  The lower dose of hormone may reduce certain side effects, however because it is a device which is implanted into the uterus, it causes other risks.

Mild-to-moderate side effects of Mirena may go away with time and include:

  • Irregular menstrual period, bleeding or vaginal discharge
  • Acne
  • Nausea
  • Abdominal discomfort or bloating
  • Weight changes
  • Mood changes
  • Breast tenderness
Mirena Complications

Serious side effects or complications of Mirena may be permanently damaging or even life threatening.

Complications related to Mirena as an implanted intrauterine device include:

  • Device migration – if the device becomes dislodged it may be expelled or migrate deeper into the uterus. Device migration may result in uterine or other organ perforation or may increase the risk of Mirena-related pregnancy.
  • Organ perforation – if the device migrates into the uterus, it may perforate or penetrate the uterine wall. If left untended, it may travel through the uterus into the abdominal cavity and damage other organs.
  • Ectopic pregnancy – though Mirena is 99% effective at preventing pregnancy, migration may make pregnancy more likely. Up to half of all pregnancies that occur with Mirena may be ectopic or occur outside of the uterus. Ectopic pregnancy generally must be surgically removed and may be a medical emergency.
  • Pelvic infection – pelvic inflammatory disease may occur with Mirena implantation in the uterus. The risk is more likely if Mirena is implanted with an existing vaginal or gynecologic infection and is highest within a few weeks after implantation.
  • Bleeding – bleeding that is heavy or begins suddenly may indicate a complication such as organ perforation or ruptured ectopic pregnancy has occurred and may require treatment as a medical emergency.


Mirena is a hormonal intrauterine device (IUD) made by pharmaceutical giant, Bayer Healthcare which was approved in 2000 in the U.S.  It is implanted in the uterus and left in place for up to five years.  Mirena is made of a type of plastic, known as medication-eluting plastic, which contains the contraceptive hormone levonorgestrel.

Once implanted in the uterus, the flexible device expands to form a “T shape” which allows it to remain in the uterus.  Over a 5-year period, the plastic will slowly release levonorgestrel into the uterus to prevent pregnancy by making the uterus inhospitable to a fertilized egg.

Mirena is said to be over 99% effective at preventing pregnancy but may cause side effects. Most side effects are mild to moderate and will go away with time, but others may be serious or even life-threatening.

How Mireuna IUD Works

Levonorgestrel is a progestin hormone used for birth control that is usually taken by mouth as an oral contraceptive.  It has also been used in other birth control devices such as Norplant and in birth control patches. Mirena is constructed of a type of plastic which is embedded with levonorgestrel to be released slowly over a long period of time, directly into the uterus at a rate of 20mcg/day.

Levonorgestrel in Mirena released into the uterus works by:

  • Altering or thinning the uterine wall
  • Thickening cervical mucus to prevent any sperm from entering the uterus
  • Decreasing the survival rate of sperm

It may also prevent ovulation due to systemic or body-wide absorption of levonorgestrel, similar to the way oral contraceptives and other levonorgestrel devices work.

Because Mirena releases levonorgestrel into the uterus rather than into the bloodstream, Mirena uses a smaller amount of hormone than birth control pills, implants or patches which may reduce certain side effects, however because it is implanted into the uterus, it causes other risks. 

Mirena Implantation Procedure

Mirena is implanted by a physician and will last up to five years.  When the woman wishes to remove it or it is time for replacement, the removal must also be done by a healthcare provider.

Implantation of Mirena is performed through a special tube-like device where it is inserted through the cervix.  Once in place, flaps on the IUD will expand and hold the device in the uterus to begin releasing hormone.  A string is left in place, protruding through the cervix which will allow the recipient to check to ensure that the device is present and will later allow for removal.

Mirena is removed by pulling the attached string, which causes the flexible arms to bend to allow the device to slide out of the cervix.  In some cases, however, the device can migrate or move out of the uterus or become implanted in the uterine wall or to perforate the uterus and other abdominal organs.  This will require surgical removal. Surgical removal could lead to permanent damage.

History of Mirena and IUDs

The IUD became widely available in the U.S. in the 1950s when thermoplastics allowed for easy insertion and removal of flexible plastic. Their popularity increased in the 1960s with the introduction of the copper IUD and by 1973, an estimated 10% of women using birth control had an IUD.

Unfortunately, one of the most popular devices on the U.S. market had a serious design flaw. It had a porous monofilament string which allowed for bacteria to grown on the device, resulting in thousands of infections, hospitalizations, septic abortion events and at least 5 deaths.

The Dalkon Shield was withdrawn from the U.S. market in 1975 but sales of other IUDs in the U.S. plummeted as well. By the mid-1980s, more than 300,000 lawsuits had been filed against A.H. Robins, manufacturer of the Dalkon Shield and all other manufacturers simply quit making their devices.

Outside of the U.S. women had continued to use IUDs as a preferred contraceptive method and the first hormone-emitting device, progenitor of Mirena, was introduced to Europe in the mid-80s. Its introduction to the U.S. market in 2000 brought a renewed popularity for women who wanted longer-term birth control. The first hormonal IUD, Progestasert was withdrawn only a year after its introduction. Mirena was the only available hormonal IUD in the US until 2013 when the FDA approved Skyla, a lower level levonorgestrel IUD that is only good for three years.

Mirena is used by over 150 million around the world. In the U.S., about 5 percent of women who use contraceptives, use IUDs. Women living outside the US are at least twice as likely to use an IUD. In 2009 Mirena was approved to treat heavy menstrual bleeding in women already using an intrauterine device.

Side Effects and Complications of Mirena

Because Mirena is a hormonal birth control method, some side effects are related to the hormone.  In addition, however Mirena is a medical device which is implanted in the uterus and may cause complications relating to the device.

Most side effects of Mirena are not severe and will go away with time, however some adverse events caused by the device can be serious or even life-threatening.

Mild side effects include:

  • Local irritation
  • Irregular menstrual period and vaginal discharge
  • Acne
  • Weight changes
  • Mood changes
  • Nausea
  • Breast tenderness

More severe side effects of Mirena can be permanently damaging or even life threatening.

Mirena and Infections

Implantation of an intrauterine device such as Mirena may increase the risk of pelvic infection, especially within the first three weeks after insertion.  Pelvic Inflammatory Disease (PID) is a bacterial infection that can result in damage to the female reproductive organs and may result in infertility.  Women who have PID are more likely to have it again and should not use Mirena or any IUD.

Mirena and Device Expulsion

Mirena may be spontaneously expelled from the uterus.  About six percent of Mirena users experience expulsion. This may cause tissue tearing or other damage and result in bleeding.  Symptoms may include bleeding, spotting, cramping, and pain during sexual intercourse.  A routine check of the device string may indicate a shorter, lengthened or absent string.  A woman who experiences expulsion will not be protected from pregnancy.  Women without a child have a higher risk for expulsion of Mirena.

Mirena and Pregnancy Complications

Mirena is reported to be effective at preventing pregnancy over 99% of the time.  If a pregnancy occurs however, the presence of hormones may damage a developing fetus which may result in miscarriage and may cause the uterus to become infected or septic, resulting in a septic abortion, an extremely dangerous condition.  If a pregnancy is allowed to proceed, there is a high risk of premature birth.  If a pregnancy occurs during Mirena use, it is recommended that the woman undergo surgical zygote removal.

Though pregnancy is rare with Mirena use, an estimated half of Mirena-related pregnancies are Ectopic pregnancy.  An ectopic pregnancy is often called “tubal” pregnancy as it often involves fertilized egg implantation in one of the fallopian tubes but may occur in the cervix or other areas outside of the uterus.  

An ectopic pregnancy is generally considered a medical emergency and often requires surgical removal of the fallopian tube which can result in infertility.  Women who have had a previous ectopic pregnancy are at higher risk and should not use Mirena.

Mirena and Device Migration

In addition to device expulsion, Mirena can migrate from its normal position further into the uterus.  This may cause perforation of the uterine wall.  If the device perforates the uterine wall and enters the abdominal cavity, it may damage the bladder, blood vessels, intestines and other organs.  This can result in serious pain and infection.

Mirena device migration will often require surgical removal.  In some cases, the surgery must be conducted as an emergency procedure if the patient’s life is threatened.  Damage from device migration and surgical removal may be permanent and result in infertility.  Some women may also require multiple surgeries to locate and remove the device and repair damage to organs and other tissue.

Women who use Mirena within six months after birth may be more likely to experience device migration.

Mirena Warnings and Lawsuits

Since 2004, the FDA has received over 47 thousand reports of adverse events related to Mirena use.  In 2009, the FDA issued a warning to its manufacturer, Bayer for overstating the effectiveness of the device and minimizing risks.  Bayer had claimed in its “Simple Style” live marketing talks targeting “busy moms” that the IUD would help women with increased libido and that they would “look and feel great”.

As shared in the warning letter, at least 5 percent of women using the Mirena IUD had are reporting decreased libido during clinical trials.  The Division of Drug Marketing, Advertising, and Communications (DDMAC), a department of the FDA that reviews marketing plans and documents of pharmaceuticals had concluded that this program overstated Mirena benefits, while downplaying side effects.

Bayer has also been warned by the FDA regarding advertising for some of its other birth control products including Yasmin and Yaz oral contraceptives.

Hundreds of lawsuits have been filed against Bayer regarding Mirena.  Some victims have received compensation for their injuries, but others may still be pending.

Notwithstanding claims relating to this product, the drug/medical device remains approved by the U.S. FDA.