Why You Might Prefer a Mirena IUD Over the Pill

The pill, the patch, the ring — they're all great in theory, but if you constantly forget to take your pills or hate the waiting period for both the patch and ring, these might not be the best choices for pregnancy prevention. For a more long-term form of birth control, many women are using the Mirena.

What it is: The Mirena is a type of intrauterine device (IUD) that is placed inside your uterus by a health-care provider to prevent pregnancy for up to five years. It's a T-shaped piece of soft, flexible plastic less than 1.5 inches long that emits a small amount of progestin directly into your uterus (it's estrogen-free). There are two threads attached to the end that hang down out the opening of your cervix to help you check whether it's in the correct place.

Effectiveness: It's 99-percent effective at preventing pregnancy, but like the pill, it won't protect against STDs such as HIV. It is effective immediately if inserted within seven days after the start of your period, otherwise you'll need a backup form of birth control for the first seven days after getting the Mirena.

How it works: The small amounts of levonorgestrel (a type of progestin) released by Mirena thicken your cervical mucus to prevent sperm from entering your uterus so they can't reach your egg, and thus can't fertilize it. It also thins the lining of your uterus, and may stop the release of your egg from your ovaries. In the unlikely event that a sperm does fertilize your egg and it survives, an IUD causes inflammation of the uterus making it harder for the fertilized egg to implant. To ensure the Mirena remains in place, insert a finger into your vagina, feel for the cervix, and check for the threads once a month.

Who should use it: Since this is a long-term form of birth control, it's recommended for women who aren't planning on having children for several years, are done having children, or don't want to have children. Since it doesn't offer protection against STDs, it's recommended for women who are in long-term relationships with someone they know is STD-free.

The pros: Insertion only takes a few minutes and it'll prevent pregnancy for up to five years. After a year of use, one out of every five users will have no period at all — think of all the money you'll save on pads and tampons! If you need birth control for longer than five years, you can choose to have another one inserted after the first one is removed. It's also easily reversible, which means if you decide you want to become pregnant, just have the Mirena removed and you can start trying right away. Since the hormones stay in the uterus, it won't cause significant weight gain like oral contraceptives sometimes do or increase breast tenderness.

The cons: Insertion can be very painful and can cause some women cramping, bleeding, and dizziness. Some women complain of irregular periods, spotting, and some have heavy bleeding for the first several months of use. IUDs also increase the risk of pelvic inflammatory disease (PID), although the percentage of women using the Mirena who develop PID is less than one percent. A rare life-threatening infection called sepsis could also occur within the first few days after Mirena is placed. The Mirena could also become embedded in the uterine wall, or even perforate it, and in either case, the user would no longer be protected from pregnancy, and the Mirena would need to be surgically removed. Another not-so-great thing about the Mirena is that since the threads hang down out the opening of your cervix, your partner may be able to feel them during intercourse.

How it differs from ParaGard IUD: The ParaGard contains copper and is completely hormone-free, so it won't interfere with your natural menstrual cycle. This is good news for women who don't want to take hormones and who like getting their monthly period to let them know they're not pregnant. Some women experience heavier periods or spotting while using the ParaGard, but this usually subsides after three months. Like the Mirena, it's also 99-percent effective at preventing pregnancy and is effective immediately after insertion, regardless of where you are in your cycle. The ParaGard, however, lasts twice as long as the Mirena, for up to 10 years.

How it differs from Skyla IUD: Another hormone-releasing IUD, it works just like the Mirena and is also 99-percent effective at preventing pregnancy. It's just over one inch, so it's slightly smaller than the Mirena and needs to be replaced every three years. Irregular spotting and periods may occur for the first three to six months, but after that, many women experience shorter, light periods or no periods at all.