Risks of the Mirena Coil

Updated April 13, 2018

The Mirena coil is an intrauterine device (IUD) that can help prevent pregnancy for up to five years. The Mirena coil is also used to treat heavy menstrual bleeding. Mirena is recommended for women who have at least one child. Serious complications are rare, but Mirena does carry risks. Patients considering Mirena as a birth control option should talk with their doctors to decide if it is a safe method for them.

Ectopic Pregnancy

Though the risk of pregnancy is rare for women using Mirena for birth control, about half of all pregnancies that occur in patients with Mirena are ectopic pregnancies. An ectopic pregnancy can cause a loss of fertility and women who have had one ectopic pregnancy are more likely to have another.

Intrauterine Pregnancy

A woman who gets pregnant normally with an intrauterine pregnancy while using Mirena should have the IUD removed. Removing Mirena may result in a miscarriage. If the IUD is not removed, the risk of miscarriage still increases. Premature labour and delivery may occur if Mirena is not removed. A septic abortion that occurs because of an infection in a pregnant woman with an IUD in place can result in septic shock or death.

Pelvic Inflammatory Disease

IUDs increase the risk of pelvic inflammatory disease (PID). PID can cause damage that can lead to infertility, hysterectomy or death. The highest risk of developing PID is usually within the first 20 days after insertion, according to Women who have had PID or suspect they have PID should not use IUDs for birth control.

Irregular Bleeding

Mirena can cause spotting and other irregular and heavy bleeding patterns. Irregular bleeding is most common in the first three to six months after insertion. After six months, the number of bleeding days usually decreases and bleeding starts to regulate. Irregular bleeding patterns may continue beyond six months in some individuals. Women who do not menstruate within six weeks of their last menstruation should see a doctor to rule out pregnancy.


Mirena can become embedded in the uterine wall in some women. Embedment increases the risk of pregnancy. Embedded IUDs should be removed, but they sometimes require surgical removal depending on how deep in the uterine wall they are.


Mirena can puncture or perforate the uterine wall or cervix during the insertion process, but the perforation may not be detected until later. Perforation can cause the IUD to migrate outside of the uterus and necessitate surgical removal. Women should wait at least six weeks after delivery to have an IUD placed because perforation is more common when Mirena is inserted in women who are lactating or have recently given birth.

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About the Author

Amanda Knaebel is a self-professed gadget geek and loves all things tech, both new and old. Amanda has been working as a freelance writer for over 10 years on topics including technology, health, fitness, nutrition, gardening and many more. She has also worked with Fortune 50 tech and financial companies, both in technical support and content production.