is an intrauterine contraceptive (IUC) used to prevent pregnancy. It is a small, flexible plastic device that slowly releases levonorgestrel (a progestin hormone) into the body. It is inserted into the uterus and left in place for up to five years. Although the contraceptive is usually very effective, pregnancies may occur, but this is rare. Mirena can cause problems in these pregnancies.
Mirena and Pregnancy Category X
The U.S. Food and Drug Administration (FDA) uses a pregnancy category system to classify the possible risks to a fetus when a specific medicine is taken during pregnancy. Pregnancy Category X is given to medications that should not be used during pregnancy. Often, this is due to problems that could potentially occur, such as miscarriages or birth defects. All hormonal contraceptives (including birth control pills
, patches, rings, and Mirena) are classified as pregnancy Category X medications.
An ectopic pregnancy
is a pregnancy that occurs outside of the uterus (including a "tubal" pregnancy). Although pregnancy is rare in women who use Mirena, women who do become pregnant while using Mirena have a high risk of ectopic pregnancy. About half of all pregnancies in women who use Mirena are ectopic. These pregnancies cannot survive, often require surgery, and can result in permanent damage that can lead to infertility. Be watchful for any signs of an ectopic pregnancy, such as severe abdominal pain (stomach pain) accompanied by unusual vaginal bleeding. You should not use Mirena if you have ever had an ectopic pregnancy or if your healthcare provider feels that you are at risk for an ectopic pregnancy.
Because of the high risk of ectopic pregnancy (and because waiting to take care of an ectopic pregnancy can be very dangerous), let your healthcare provider know immediately if you become pregnant (or even suspect that you might be pregnant) while using Mirena.