How it Works
Mirena and the Menstrual Cycle
Mirena Safety
Women Who Should Not Use Mirena
Mirena and Future Pregnancy
Insertion of the IUD
If You Think You're Pregnant...
Other Uses for Mirena
Introduction
Mirena is an intrauterine device (IUD) that is inserted into the uterus to prevent pregnancy. It is made of plastic, formed in the shape of a 'T' and is about the size of a quarter. It contains a small amount of a hormone, levonorgestrel, which is released continuously while the device is in place. Mirena is extremely effective in preventing pregnancy - fewer than 1 in 100 women using it will become pregnant.
How it Works
Mirena affects the body in a number of ways to prevent pregnancy, and it is likely that a combination of factors is responsible for Mirena's contraceptive effect:
Mirena thickens the mucus at the entrance to the uterus, thus blocking sperm entry.
Mirena inhibits ovulation (release of an egg), although not always 100%.
Like all IUD's, Mirena creates an environment within the uterus that limits sperm survival and prevents fertilization.
Mirena and the Menstrual Cycle
Mirena thins the lining of the uterus leading to lighter menstrual flow, so in general, you can expect to have less menstrual blood loss while using Mirena. However, during the first three to six months, you may have irregular and frequent bleeding as your body adjusts to the IUD. After that, your bleeding will most likely become lighter and less frequent. After six months of use, about half of women stop having periods, although light spotting occurs on average about three days per month. After one year of use, 20 percent of women stop having periods altogether. This makes Mirena an attractive alternative for women who may have painful periods, or heavy or prolonged menstrual flow.
If you are bothered by the idea of not having your period, or do not like to experience any shift in your menstrual pattern, then Mirena may not be the best option for you. On the other hand, if you are bothered by heavy, irregular or painful menstrual flow, Mirena may be a good option.
There are currently two other IUDs available in the United States: the Para Gard IUD and the Progestasert IUD. ParaGard is effective for up to ten years, but unlike Mirena, may cause heavy menstrual flow or cramps. The Progestasert, like Mirena, contains a progestin hormone, but this device needs to be replaced annually. If you have had heavy bleeding or cramps while using the ParaGard IUD, or have heavy periods or severe menstrual cramps, Mirena may be a good choice for you.
Mirena Safety
Levonorgestrel, the hormone contained in Mirena, has been used in birth control pills for decades, although the dose found in Mirena is much lower than in birth control pills.
IUD's have been used for many years to prevent pregnancy. In the past, there were problems with some IUD's due to design flaws and use in women at risk for sexually transmitted infections. Since then, changes in IUD design and careful evaluation of which women are best suited for the device, have made IUD's an extremely safe form of birth control, much safer than pregnancy itself can be. But remember that IUD's are safest when used by women in long-term, monogamous relationships.
As with all IUD's, there is a small risk - about 1 in 1000 - of infection associated with the Mirena insertion. This is because the vagina, like the mouth, is colonized with bacteria. If these bacteria gain access to the normally sterile uterine cavity during IUD insertion, infection may result. The risk of infection persists for about 6 weeks after the insertion. For this reason, your doctor cleanses the cervix with antiseptic prior to the insertion, and may delay the procedure until any existing vaginal infection is cleared. To try to prevent infection, some doctors prescribe antibiotics at the time of IUD insertion. But this may not be necessary for women with low risk of sexually transmitted diseases, as this practice has not been found to decrease their risk of infection.
Signs of infection after IUD insertion include pelvic pain, fever, heavy bleeding or new vaginal discharge. Be sure to notify your doctor if any of these symptoms occur.
Other side effects
About ten percent of women using Mirena report some lower abdominal cramps. Less than five percent complain of breast tenderness, acne, or mood changes.
Women Who Should Not Use Mirena
Women with multiple partners, or whose partners have outside sexual relationships, should not use Mirena or any other IUD. These women are at risk for acquiring sexually transmitted diseases that can lead to serious pelvic infections if an IUD is in place.
Women with the following conditions are also advised not to use Mirena:
- Previous ectopic pregnancy, or high risk for ectopic pregnancy (for example, women with blocked fallopian tubes)
- History of pelvic inflammatory disease (PID)
- Congenital malformation of the uterus
- Large fibroids, or fibroids of any size that distort the uterine cavity
- Active liver disease or liver tumors
- Allergy to levonorgestrel, silicone or polyethylene
- Known or suspected breast cancer
- Recent post-partum or post-abortion infection of the uterus
- Leukemia, AIDS or other conditions that predispose to infection
Women with the following conditions may use the IUD, but require special precautions and/or monitoring:
- Diabetes (Levonorgestrel can affect blood sugar levels.)
- Heart disease or heart valve problems
- Blood clotting problems or medications that reduce blood clotting
- Breastfeeding or recent pregnancy
- Chronic use of steroids or other drugs that may predispose to infection
Mirena and Future Pregnancy
Women who attempt pregnancy after using Mirena have the same rates of pregnancy as normal couples; about 80% will become pregnant within one year.
I generally recommend that you wait until you have had a child before using an IUD. Women who have not yet given birth generally have higher rates of expelling IUDs, and may have more cramping during IUD use. Also, although the risk of pelvic infection from IUD insertion is rare, most physicians would advise against taking any risk until you have had at least one child.
If you are planning a pregnancy within the next year, you may wish to use a shorter acting form of birth control, such as birth control pills, barrier methods or Lunelle.
Mirena and Breastfeeding
Mirena is safe for both mother and baby. Although small amounts of levonorgestrel can be detected in breast milk of Mirena users, infants exposed to low levels of progestins have not been found to have any impairment of growth or development.
Insertion of the IUD
Insertion is performed in the doctor's office - generally, but not always, during a menstrual period - and takes only a few minutes.
Your physician will make sure you are not already pregnant, usually by doing a urine pregnancy test. You will be examined to rule out infection or other problems contraindicating IUD use. A speculum will be inserted into your vagina, and your cervix will be cleansed using an antiseptic solution. Your physician will measure the depth of your uterus and will then insert the IUD through a thin plastic tube. That's it!
Often there is mild cramping, but serious pain is uncommon. Rarely, some women will have dizziness after the insertion. Your doctor may advise you to take pain medication such as Motrin or Advil prior to the procedure.
How do I know the IUD is in place?
You should not feel the IUD once it is in place. You partner may notice the strings during sexual activity, but this is unusual. You should feel for the strings of the IUD after each menstrual cycle, or about once a month if you do not menstruate while using Mirena.
If you go more than six weeks without a period, get a pregnancy test. After that, unless you have signs or symptoms of pregnancy, testing is not needed, since it is extremely unlikely that you will become pregnant while using Mirena, especially if your menstrual cycle is suppressed.
If You Think You're Pregnant...
If you think you are pregnant, contact your physician immediately. If a woman does become pregnant using Mirena, there is about a 50 percent chance that the pregnancy will be in the fallopian tube (ectopic pregnancy). However, because Mirena is so effective at preventing pregnancy in the first place, women using Mirena actually have fewer ectopic pregnancies than women using less effective methods of birth control or women who are not using birth control at all.
If the pregnancy is in the uterus and you plan to continue it, the IUD should be removed immediately. Otherwise, Mirena can be removed at the time of a planned abortion.
Other Uses for Mirena
Researchers are studying whether or not Mirena can be used to provide the progesterone component of hormone replacement for menopausal women. It is also being studied as a treatment for dysfunctional uterine bleeding. However, Mirena is not currently FDA approved for these uses.
