The Mirena is a type of IUD (intrauterine device) that is placed inside your uterus (by a doctor or nurse practitioner) to prevent pregnancy for up to five years. It's a T-shaped piece of plastic that emits hormones into your uterus directly. The hormones stay in the uterus and are not systemic, meaning they do not go to other parts of your body. This is why it won't cause significant weight gain like oral contraceptives sometimes do or increase breast tenderness. Another bonus is that the Mirena might also shorten, lighten, or even eliminate periods altogether while you use it.
OK, but how does Mirena work? The small amounts of levonorgestrel released by Mirena make your cervical mucus thick and tacky so sperm can't swim through it. If the sperm gets in, then they can't make it to the egg to fertilize it.
Another way the Mirena, or IUDs in general, prevent pregnancy is it promotes the production of white blood cells and when a foreign object is placed inside the uterus, your body creates these white blood cells to defend itself. So when you have sex, if sperm does make it through your tacky mucus to your uterus, the white blood cells will attack them.
Interested in how effective it is? To see the stats, just
Mirena is 99.9 percent effective at preventing pregnancy and like metal IUDs, it needs to be fitted and removed by a medical professional, but once it's in place, that's it, you're done, no fuss, no muss!
Dear's Advice: Mirena is great if you are looking for hassle-free birth control for up to five years straight. Just a reminder, it does not prevent against STIs, so that's why it's great to use if you are in a long-term relationship with someone you know is disease-free.
It's also a great option if you've already had kids and aren't planning on having anymore, or if you know it's going to be many years before you want to start a family. If this interests you, ask your doctor about Mirena.