Intrauterine devices, shortened as IUDs, are one form of pharmaceutical birth control. There are two types of IUDs: copper and hormonal. Mirena IUDs are hormonal, as they contain a form of progestin. Copper IUDs contain no hormones.

Both types of IUDs are popular in the U.S. due to their low maintenance and long efficacy in preventing pregnancy. Once the IUD is inserted, patients typically have small side effects and don’t have to remember to take a drug on a daily or otherwise regular basis. IUDs offer long-term contraceptives: once they are implanted in the uterus, they continue to prevent pregnancy for up to 5 or 10 years, depending on the type.

While not the most popular form of birth control, IUDs are the most effective form of contraceptive. Their failure rates are 0.8 percent for copper IUDs, and 0.2 percent for hormonal IUDs. These failure rates are significantly lower than other hormonal methods of contraception, including pills, patches, and shots, which range from 5 to 9 percent failure rates.

Purpose of Mirena IUD

The Mirena IUD is a small, T-shaped piece of plastic which contains levonorgestral, a type of progestin. This hormone works locally to prevent pregnancy, unlike other hormonal methods where the hormone effects the entire body. The IUD release small amounts of progestin daily to prevent pregnancy. The device is inserted into a woman’s uterus by a physician; the method is very simple and routine, taking less than a few minutes. The Mirena IUD is intended primarily for women who have already had at least one child.

Once implanted, the IUD may thicken the mucus in the cervix, which decreases the chance of sperm reaching the egg. It also thins the uterus lining. A thinner uterus lining also decreases the chance of pregnancy.

Based on the FDA’s approval of Mirena IUDs, a device may be used for up to 5 years. After that, the device should be removed. To continue use as a contraceptive, a new IUD should be implanted. The device can be removed at any time, making conception possible within a month of removal.

Mirena IUD Safety Concerns

Mirena IUDs are generally quite safe for most women using the device. However, in 2010 the FDA provided strict warning after Bayer, the manufacturer, failed to communicate inherent risks and side effects of using Mirena IUDs, thereby promoting more efficacy than is accurate.

Uterine Perforation and Severe Medical Problems

Severe side effects have been documented by patients, though these are not common.

In some cases, the IUD has broken into smaller pieces, which can lead to uterine perforation. Further, whole migration of the IUD can also lead to uterine perforation. If the IUD has migrated from its point of insertion, pregnancy protection effectively ceases.

Mirena IUDs also increase the risk for pelvis inflammatory disease and severe infection. Ectopic pregnancies and ovarian cysts have also been associated with the use of Mirena IUDs.

Irregular Bleeding and Lack of Periods

Mirena IUDs have more common, less serious side effects that, while non-life-threatening, can cause alarm or concern in patients who are unaware of the risks. It is common that Mirena can lead to irregular bleeding for the first few months after the IUD is implanted. Beyond those months, the period can cease altogether, known as amenorrhea. Patients unaware of this side effect may question the drug’s efficacy in preventing pregnancy.

Other common side effects include abdominal and pelvic pain.

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FDA Warnings Regarding Marketing of Mirena IUDs

Part of the FDA’s regulatory role is ensuring that promotional materials disclose risk and other pertinent data about the drugs or medical devices. Without this disclosure, the manufacturer may be misleading the public about the efficacy and/or consequences of the drug in its suggested use.

In April 2009, the FDA warned Bayer and the public about the company’s misleading representation regarding the efficacy of Mirena IUDs. The FDA indicated that Bayer wholly failed to communicate any risk whatsoever to consumers.

Specifically, Bayer’s initial marketing for Mirena IUDs failed to indicate that Mirena should only be used for up to 5 years before replacement, implying to the public that the device can be used indefinitely. Bayer further failed to market that Mirena is most recommended for women who have had at least one child, thereby implying that the device is suitable for all women.

Today Mirena IUDs are primarily recommended for women who have had at least one child.