Can You Get Pregnant with an IUD?

Whether you're going on birth control for the very first time or are looking to switch up your contraception, you probably have a detailed checklist of features to consider before settling on the best one for your body. You should take into account how the contraceptive would fit into your lifestyle, how often you'll need to use it, any potential side effects, and, perhaps most importantly, how effective it is at preventing pregnancy.

For some folks, an intrauterine device (IUD) is as a strong contender, thanks to its set-it-and-forget-it style and long lifespan. But what are the chances of pregnancy with an IUD, exactly? Here, an ob-gyn breaks down what you need to know about IUDs and pregnancy, including the likelihood of conceiving while using the contraceptive and the main signs of pregnancy with an IUD.

What's an IUD, anyway?

In order to fully understand the chances of pregnancy with an IUD, you need to know how this form of contraception works in the first place. An IUD is a small, T-shaped, plastic device that's placed inside the uterus by a doctor to prevent pregnancy, according to the Centers for Disease Control and Prevention. "There are different types of IUDs that work in different ways, but they all work to prevent sperm from being able to make their way up through the uterus to fertilize an egg," says Kelly Culwell, M.D., a board-certified ob-gyn known as Dr. Lady Doctor.

Specifically, a progestin-releasing IUD — unsurprisingly — releases the hormone progestin, which prevents the ovaries from releasing an egg; thickens cervical mucus, thus hindering sperm from entering the uterus; and thins the lining of the uterus, making it more difficult for a fertilized egg to attach, according to the U.S. National Library of Medicine. This type of IUD starts preventing pregnancy within seven days after being inserted and can stay in the uterus for three to eight years, depending on the brand, according to the NLM. A copper-releasing IUD, on the other hand, is hormone-free, prevents pregnancy by releasing copper ions that are toxic to sperm, starts working immediately after being inserted, and lasts up to 10 years, according to the NLM. Plus, both types of IUDs use their T-like shape as a form of back-up protection, as it physically helps block sperm from reaching an egg, according to the NLM.

What are the chances of pregnancy with an IUD?

Thankfully, the odds of conceiving with an IUD inserted is extremely low. "IUDs are very effective," says Dr. Culwell. "In general, less than 1 percent of women with an IUD get pregnant each year." In fact, the five brands of IUDs approved by the Food and Drug Administration for use in the U.S. (Paraguard, Mirena, Kyleena, Liletta, and Skyla) are all more than 99 percent effective at preventing pregnancy, according to the companies.

That said, no birth control is 100 percent effective, says Dr. Culwell. "Rarely, even with an IUD in place, a sperm is able to make its way through the uterus and into the fallopian tube to fertilize the egg," she adds. There are a few factors that may increase the likelihood of pregnancy with an IUD inserted, too, says Dr. Culwell. A device that isn't placed correctly in the uterus (think: it's located away from the top portion of the uterus or it's rotated) may be less effective, according to a 2015 article published in Ultrasonography. Pregnancy is also more likely if the IUD is "expelled out of the cervix and vagina" — meaning it's no longer in the uterus and can't work it's magic — which is most common in folks who have the device inserted immediately after giving birth, says Dr. Culwell. And in rare cases, the IUD can perforate through the wall of the uterus while being inserted, "which means that it is not inside the uterus and therefore not able to prevent pregnancy," says Dr. Culwell. When this occurs, you might experience persistent, mild lower abdominal pain, and you'll generally need to have the device surgically removed, according to an article published in Open Access Journal of Contraception.

Of course, you can further minimize the chances of pregnancy with an IUD by also using condoms, which have a 13 percent typical failure rate, according to the CDC. This form of contraception blocks sperm from entering the uterus — and thus prevents pregnancy — and, unlike IUDs, also prevents STI transmission, per the CDC.

What are the signs and risks of pregnancy with an IUD inserted?

As with other forms of birth control (think: the pill, the ring), you typically still get your regular period while using a non-hormonal copper-releasing IUD, so a missed visit from Aunt Flo may be the first sign you're pregnant, says Dr. Culwell. But the signs might not be so blatant if you're using a progestin-releasing IUD, as they can often cause light, irregular, or absent periods, she says. "Relying on your period to be sure you are not pregnant may not be possible," she says. In both cases, you'll also want to watch for symptoms such as nausea, bloating, tender breasts, fatigue, and pelvic or abdominal pain if you think you may be pregnant, she says. The catch: "These symptoms aren't specific to pregnancy, so if you are concerned at any point about pregnancy, you should take a home pregnancy test and/or contact your health-care provider," says Dr. Culwell.

And you'll want to do so ASAP. Becoming pregnant with an IUD inserted runs the risk of miscarriage and infection, says Dr. Culwell.More significantly, it increases the risk of an ectopic pregnancy — a life-threatening pregnancy that occurs outside of the uterus, most commonly in the fallopian tube, and can't be carried to birth term. Instead, the developing cells need to be removed to save the person's life, according to the NLM. That's why providers typically recommend removing an IUD as soon as a pregnancy is detected, says Dr. Culwell. Case in point: One study found that eight in 10 pregnancies resulted in miscarriage when the IUD was left in place, but removing it reduces the risk of miscarriage, preterm delivery, and infection, according to the CDC. If you decide to not continue with the pregnancy, you'll likely still need to have your IUD removed first, per the Department of Health in Victoria, Australia. (BTW, it's not a good idea to remove your IUD at home.)

If your IUD's strings have traveled up from the vagina into the uterusand your provider determines they can't be safely retrieved, removing the device while pregnant may not be an option, says Dr. Culwell. In those cases, your doctor may leave the IUD in place, as searching for the strings could "inadvertently injure" the expectant parent, according to The University of Texas Southwestern Medical Center. They will typically advise you to seek medical care if you have heavy bleeding, cramping, pain, abnormal vaginal discharge, or fever — potential signs of miscarriage, sepsis, or premature labor or delivery, according to the CDC. (FTR, "missing strings" — IUD strings that are not visible or felt in the vaginal canal — can happen regardless of pregnancy status, and when you're not expecting, they can generally be retrieved in your doc's office with the use of proper tools and anesthesia, according to an article published in Contraception.)

The TL;DR on pregnancy and IUDs.

Becoming pregnant with an IUD inserted is "exceedingly rare," according to an article published by the NLM, and it's still one of the most effective forms of contraception. The pill, the patch, and the hormonal vaginal ring, for example, all have a typical use failure rate of 7 percent — compared to less than 1 percent for IUDs, according to the CDC. That said, there isn't one "best" form of birth control, and your needs may change over time, per the Office on Women's Health. So if those risks of pregnancy with an IUD inserted make you feel uneasy, chat with your doc about your other birth control options. (Next up: Annie Murphy of 'Schitt's Creek' Wants You to Consider — and Question — All Your Birth Control Options)