IUD 101: What to know about this form of birth control

Story highlights

  • An IUD is more than 99% effective and can prevent pregnancy for up to 12 years
  • Some versions make periods lighter or nonexistent

(CNN)IUDs, or intrauterine devices, are more than 99% effective in preventing pregnancy, and some can work up to 12 years, but a 2016 survey from the Urban Institute found that many women still don't know anything about these longer-acting reversible contraceptives. Here's what you need to know.

What is an IUD?

IUDs are tiny, the size of a quarter or smaller, and shaped like a "T." They are made out of flexible plastic.
    Unlike pills or other birth control methods that women can administer on their own, this one requires the help of a medical professional who will insert it into the woman's uterus.
    The woman may get a medication first to help open the cervix and to numb it to limit discomfort. The professional will then insert a speculum into the vagina to make room for a tool with the IUD. The IUD will go through the opening of the cervix and into the uterus.
    The procedure takes about five minutes.

    How do IUDs work?

    An IUD forms a barrier that keeps a man's sperm from interacting with a woman's egg, preventing conception. It physically changes the way the sperm cells move in two ways, depending on the type of device.
    The US Food and Drug Administration has approved five brands: Skyla, Liletta, Kyleena, Mirena and ParaGard.
    The ParaGard device is wrapped in copper. Sperm don't like copper, which interferes with the way they function and will keep the sperm from interacting with an egg. This device can prevent pregnancy for up to 12 years and starts to work right away.
    All the other devices use the hormone progestin. It's similar to progesterone, which a woman's body makes naturally.
    Progestin prevents pregnancy in two ways: First, it thickens the mucus on the cervix, trapping and blocking sperm from getting to an egg. The hormone can also stop the egg from leaving the ovaries. If there is no egg released, there is no possibility of pregnancy.
    Skyla works for up to three years, Liletta works for up to four, Kyleena up to five, and Mirena can work for up to six years.
    It may take a week for the hormones to kick in after implantation, so women should ask their providers whether they should use a backup form of birth control in that first week.

    The IUD advantages

    Most anyone can use these devices, and they are among the most low-maintenance forms of birth control. Once one is inserted by a medical professional, a user doesn't have to do anything else to prevent pregnancy.
    It's considered more than 99% effective, meaning fewer than one in 100 women gets pregnant while using an IUD.
    It isn't permanent, so if a user wants to get pregnant, a nurse or doctor can quickly remove it without affecting her fertility.
    The copper IUD can also work as emergency contraception: If inserted up to five days after unprotected sex, it's nearly 100% effective in preventing pregnancy.
    Many women who have heavy periods also like the devices because a number of the hormonal versions will reduce menstrual flow, and some stop bleeding altogether.
    "If you are a woman who has heavy menstrual bleeding, they can be great for that. It's important for women to anticipate how they feel about the change in their period to choose the device that is right for them," said Dr. Anne Davis, the consulting medical director at Physicians for Reproductive Health. "With Mirena, there is almost no bleeding overall. Some women don't like that, so they are interested in another device."

    The IUD disadvantages

    For women with heavy and painful periods, the copper device may not be the best choice, as it can cause a longer or heavier period, Davis said.
    IUDs don't protect against sexually transmitted infections. Users still need a condom to reduce the chance of getting or spreading an STI.
    It can be expensive up-front. Some insurance and Medicaid cover IUDs completely or at a low cost to users, but others may not. On the high end, an IUD can cost up to $1,300. That price includes the medical exam and a follow-up visit, and because they can last so long, the price spreads out over time.
    There may be a little cramping and a few backaches right after insertion. Doctors suggest using a heating pad or over-the-counter pain medicine to ease the cramps.
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    Sometimes the IUD can slip, making pregnancy possible, but if it comes out, it can be replaced. This happens to about one in 30 women, Davis said.
    It's unlikely, but it's possible to get a bacterial infection when it is placed, and if the device is placed too far, it may require surgery to remove. That happens in only one out of 1,000 patients, Davis said.
      Davis said she has had a lot of patients asking for IUDs, especially after Obamacare made it mandatory for birth control to be covered by most insurance.
      "IUDs are a good option," she said. "Especially for women who need a reliable source of birth control for a long period of time."