Intrauterine devices (IUDs) are small t-shaped plastic objects placed in the uterus (through the cervix) to prevent pregnancy for years at a time. Doctors love them because they’re incredibly effective, but it’s understandable if you have questions about the benefits, risks, and side effects.

IUDs are “an excellent form of contraception,” says Cynthia Krause, MD, a board-certified OB/GYN at Mount Sinai. “They’re great if you’re someone that doesn’t want to take a pill every day, and they’re extremely reliable.”

IUDs are more than 99 percent effective at preventing pregnancy, according to data from the Centers for Disease Control and Prevention (CDC). They don’t provide any protection against sexually transmitted infections (like, say, internal and external condoms). They are, however, considered a “set it and forget it” method that gives you protection against pregnancy for years. Still, there’s a lot to unpack, so we’ve tapped gynecologists to share what to know before getting an IUD.

What to know before getting an IUD

How do IUDs work?

There are two types of IUDs: levonorgestrel (hormonal) or copper (non-hormonal). Unlike other forms of contraception like oral birth control pills, the vaginal ring (NuvaRing), or the shot (Depo-Provera), IUDs don’t stop ovulation. They also don’t prevent sexually transmitted infections.

Hormonal IUDs (Mirena, Liletta, Kyleena, and Skyla) are made of plastic and have a reservoir that contains small amounts of levonorgestrel, a synthetic progesterone. The reservoir “releases small amounts of the hormone locally in the uterus itself,” says Lynae Brayboy, MD, an OB/GYN and chief medical officer for menstrual tracking app Clue. “It causes the endometrium to go through a process called atrophy. And atrophy basically means that it thins the lining of the uterus. Because the lining is what’s receptive to an embryo, this makes it a non-ideal situation for a fertilized egg or an embryo to implant.”

The copper IUD (Paraguard), however, is entirely hormone-free. The frame is made of plastic, and a thin layer of copper is wrapped around the legs and base. “It causes a sterile inflammation in the uterus,” making it inhospitable to fertilization. Plus, “copper is actually toxic to sperm,” making it harder for sperm to reach an egg. The copper IUD can even be used as an emergency conception if inserted within five days of having unprotected sex.

What are the pros and cons of hormonal IUDs?

“IUDs are really a great way to do many things,” says Lynae Brayboy, MD, an OB/GYN and chief medical officer for menstrual tracking app Clue.” Hormonal IUDs can help manage heavy menstrual bleeding, painful cramps, endometriosis, fibroids, and more.

Most people with IUDs won’t feel the impact of hormonal IUD. But, if you do experience any side effects from the hormones, be sure to discuss your options with your health care provider.

What is the difference between the four hormonal IUDs?

When choosing between Mirena, Liletta, Kyleena, and Skyla, Dr. Krause says to consider your goals. Are you hoping to stop your period altogether? Do you plan to have more kids in three years? The answers to these questions might impact which IUD you get.

Dr. Krause says Mirena and Liletta are nearly identical. They both contain 52 mg of levonorgestrel. But, Mirena is approved to prevent pregnancy for up to seven years, while Liletta is approved for just six. When Liletta first came out, Dr. Krause says its selling point was that it was less expensive than Mirena. It still is, but not by much—according to GoodRX, Mirena, on average, costs around $1,100 while Liletta is just under $1,000. But if you have insurance or Medicaid, you likely won’t pay anything close to that.

Mirena and Liletta are good if you’re hoping to get rid of your period, or at least have very light periods. “There’s a little higher rate of complete amenorrhea with that one, compared to the ones that have less progesterone,” says Dr. Krause.

Kyleena has 19.5 mg of levonorgestrel and prevents pregnancy for up to five years. Skyla has 13.5 mg of levonorgestrel and prevents pregnancy for up to three years. “If someone wants to try to decrease the amount of progesterone or they’re worried about the hormone effect of the IUD, the lower dose ones are available,” says Dr. Krause.

What are the pros and cons of the copper IUD?

The copper IUD (Paragard) is completely hormone-free and prevents pregnancy for up to 10 years. It can also be used as emergency contraception for up to five days after unprotected sex (two days longer than Plan B). But, that doesn’t mean it’s symptom-free. Paragard is often associated with increased menstrual bleeding and cramping. It’s “excellent for someone that wants long-term contraception and doesn’t mind their current periods, or doesn’t mind having maybe even slightly heavier periods than what they’re having now,” says Dr. Krause.

If you already have a heavy and-or painful period, Paragard likely isn’t for you. But, it’s great if you can handle the potential of your period becoming more uncomfortable and want a hormone-free option.

“A lot of individuals have side effects with hormones,” says Dr. Brayboy. “They just can’t tolerate them. A lot of patients or individuals who prefer this option, maybe they’ve tried hormonal contraceptives, and they just haven’t been happy.”

Is there anyone who shouldn’t get an IUD?

In the past, IUDs were believed to only work for people who have been pregnant because their uteruses would be a bit bigger. However, that’s not the case. “We actually recommend long-acting reversible contraception, which IUDs are part of that group, to individuals who haven’t had a child,” says Dr. Brayboy.

That said, IUDs aren’t recommended to people with certain medical issues like an active pelvic inflammatory infection or a uterine anomaly. Chat with your health care provider to decide if the IUD is right for you.

What to expect before, during, and after IUD insertion

What is the appointment like?

Although you might be tempted to move your annual check-up if you’re on your period, it’s helpful to be on or recently finished with your period when getting your IUD inserted. It’s recommended to get an IUD inserted within the first 20 days of your cycle (day one being the first day of your period). Dr. Krause and Dr. Brayboy say this is based on anecdotal evidence that shows that the insertion could be easier and less painful during this time because the cervix is a bit dilated. As someone who has gotten an IUD inserted both when I was on my period and when not, I can say that the former was much less painful.

Depending on your pain tolerance, it can be helpful to take some pain medication an hour before your appointment. Some, especially those who have had children, might not feel much pain, while it can be pretty painful for others.

When you arrive for the appointment, you’ll likely start by giving a urine sample. “Once that’s negative, then they’ll bring you into the office or the actual examination room, and you’ll be in a gown, usually from the waist down, similar to a pap smear,” says Dr. Brayboy. “You’ll get on the bed. You’ll put your feet in the stirrups, and there’ll be an exam just to make sure they know the orientation of your uterus.” There will likely be two people in the room: a doctor or nurse practitioner to insert the IUD and a medical assistant.

What does the insertion feel like?

Your provider will insert a speculum, as they do for a pap smear, and then examine the cervix. “We’ll just look to make sure there’s nothing abnormal,” says Dr. Brayboy. “And ideally, you would have had a recent pap smear that didn’t show any evidence of cancer before this is inserted.”

Next, they’ll clean the cervix. “It feels like a scratchy tampon as we clean off the cervix,” says Dr. Brayboy. “That’s just to help decrease the risk of infection.”

Now, it’s time for the insertion. The whole process only lasts a few minutes. There will de dilators on hand if your cervix needs to be dilated. If not, you should just feel three significant cramps. The first cramp happens when they use a tenaculum, an instrument used to pull on the cervix, to straighten out the uterus and make the insertion easier. Dr. Brayboy says it’s helpful if you cough at this part to distract you from the cramp. Next, you’ll feel them measure the uterus to see how long it is to ensure the IUD will fit. Next, they put in the IUD. “The insertion catheter goes in, and basically the IUD is placed, and then the catheter comes out while the IUD remains behind,” says Dr. Brayboy.

What can you expect after the insertion?

In the days following your insertion, you’ll likely feel some cramping and experience spotting. Feel free to treat these symptoms the same way you usually treat menstrual cramps. With a hormonal IUD, Dr. Krause says to expect spotting and an irregular period for the first three to six months. People who get a hormonal IUD “might still get a regular period, but lighter, hopefully. They might get no period, but irregular spotting and bleeding, especially the first few months,” says Dr. Krause. “The main thing is they have to be prepared for it to be an unknown and irregular.” For Paragaurd, you can expect heavier bleeding and increased cramping.

Is it possible to get pregnant while you have an IUD?

IUDs are the most effective form of birth control, with failure rates of less than 1 percent. Hormonal IUDs have a 0.2 percent failure rate, and Paragaurd has a 0.8 percent failure rate.

“It’s very rare to have a failure of an IUD, meaning pregnancy, but it can happen with any method,” says Dr. Krause. “And if someone does become pregnant with an IUD in, there’s a higher likelihood  of it being an ectopic pregnancy.” An ectopic pregnancy happens outside of the uterus, often in the fallopian tubes. There is no way to carry an ectopic pregnancy to full term. “The pregnancy rate is very low, but if you become pregnant when you have an IUD, you need to present to your healthcare provider immediately,” says Dr. Brayboy.

Is the removal process complicated?

In most cases, removing or replacing an IUD is pretty straightforward—though you cannot do it yourself.  When you’re ready to have your IUD changed or removed, your provider will use forceps to pull on the IUD strings gently. When your provider does this, the IUD arms will fold in as it comes out of your uturus.

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