The Mirena IUD, used by more than 12 million women worldwide, prevents pregnancy by releasing a low dose of progesterone, which suppresses ovulation. Mirena, more than 99 percent effective at preventing pregnancy, according to the manufacturer's website, is well tolerated by most women but does carry the risk of side effects.
Common Side Effects
Most side effects of Mirena are mild and include headaches, dizziness, nausea, and changes in menstrual patterns. More serious side effects include ectopic pregnancy or Pelvic Inflammatory Disease (PID), a potentially life-threatening infection of the reproductive organs.
Symptoms of serious problems that might indicate PID or incorrect insertion include heavy, long-lasting vaginal bleeding, signs of infection such as fever or chills, and painful sexual intercourse. Your doctor might need to remove the device and even perform surgery if he determines the device has perforated your uterus or embedded into your uterine wall.
If you become pregnant on Mirena, it can have serious consequences for you and your baby. According to the manufacturer's website, 2 in 1,000 women will become pregnant each year and half of these will be ectopic pregnancies, which means the embryo implants outside the uterus.
Women who have more than one sexual partner have an increased risk of developing PID, especially in the first 20 days after insertion, according to the Mirena manufacturer's website.
Disclose any signs of infection or pregnancy and risk factors such as multiple sex partners to your doctor to give her a full picture of your suitability for Mirena before she inserts the device. Report any signs of infection or pregnancy promptly to your health-care provider.