Can you get pregnant with an IUD? It's very rare, but important to know the health risks

• Your chance of getting pregnant with an IUD is 0.1% to 0.2%.
• If you get pregnant with an IUD, it's usually because it got dislodged or was improperly inserted.
• Pregnancy with an IUD puts you at a higher risk of a serious condition called an ectopic pregnancy.

The intrauterine device, or IUD, is considered to be one of the most effective methods of contraception. These devices boast a 99% effective rate when it comes to preventing pregnancy, but no method is completely foolproof.

Though rare, you can get pregnant with an IUD. Here's what you need to know about the risks.

The chances of getting pregnant with an IUD are small

Your chance of getting pregnant with an IUD is 0.1 to 0.2 percent. That means, for every 1,000 women with an IUD, one to two of them will become pregnant, says Thomas Ruiz, MD, Lead OB-GYN at MemorialCare Orange Coast Medical Center.

Most of the time, if you get pregnant with an IUD it's because of one of the following three factors:

• The IUD is not properly placed in the uterus.
• The IUD is properly places, but your uterus contracts and dislodges the device, which you'll probably notice either because the IUD will fall out or the IUD strings will feel out of place. That's why a follow-up appointment to check placement is important, Ruiz says.
• A woman has a uterine abnormality that neither she nor the doctor knows about until it's too late.

But even with proper placement and no abnormalities, the IUD, like any other form of birth control, does not completely guarantee pregnancy prevention. "We don't always know why it happens, but it can fail," Ruiz says.

How an IUD prevents pregnancy

There are two types of IUDs - one that contains copper and one that produces progestin, which is a synthetic form of the hormone progesterone. Both create a hostile environment for sperm to prevent it from fertilizing an egg.

The copper IUD releases copper ions that inhibit sperm. Whereas the progestin from the other IUD causes changes that also decrease pregnancy risk. Specifically, your uterine lining thins and cervical mucus thickens, essentially blocking the sperm's path to an egg.

How an IUD compares to the pill

The IUD is just as effective as traditional birth control pills. But the pill is only 99% effective if it's taken at the same time every day. And that can be hard for even the most diligent person to do perfectly, Ruiz says.

Moreover, unlike the pill, the IUD is highly effective regardless of your weight, age, or medication, Ruiz says. Some antibiotic medications can make the pill less effective, and studies have shown that obesity can also decrease the pill's effectiveness.

Note: To learn more about contraceptives like the pill, read our complete birth control guide.

What happens if you get pregnant with an IUD

If you suspect you may be pregnant with either type of IUD, you should see a doctor immediately, says Felice Gersh, MD, an OB-GYN and Director of the Integrative Medical Group. That's because a pregnancy with an IUD is more likely to be ectopic, which can be life-threatening.

"People can get pregnant and if that happens, there can be significant complications, so they need to be on high alert just in case something like that should happen to them," Gersh says.

But sometimes it can be difficult to know if you're pregnant with an IUD. For example, about 50% of women with the progestin IUD stop having their periods, which makes it difficult to determine if you might be pregnant. "It is really important to be aware that it [the IUD] can fail," Gersh says.

Insider's takeaway

Look out for any abnormal bleeding or pain, which can be signs you might be pregnant with an IUD. In this case, the doctor may remove the IUD.

If you have an ectopic pregnancy, that means the egg has attached to the outside of the uterus and you will need additional medication or surgery to remove it.

However, if the current pregnancy is healthy, you can bring it to term. Just be aware that if you become pregnant with an IUD, you are at an increased risk of preterm labor, miscarriage, and infection even if the IUD is removed, Gersh says.

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