There are several factors that go into choosing the best birth control—your reproductive plans, your feelings about hormones, your experience with cramps. All methods have their pros, but when it comes to the most effective type of birth control, there’s a clear winner: long-acting reversible contraceptives (or LARCs).
LARCs—which include IUDs and implants—are between 98% and 99.9% effective at preventing pregnancy. “Long-acting reversible contraceptives are the most effective form of birth control because there's no what we call ‘user error,’” says Taraneh Shirazian, M.D., assistant professor in the department of obstetrics and gynecology at NYU Langone Health and founder of global women’s health nonprofit Saving Mothers, “meaning that you don't have to do anything [in order for them to work].” Over time, that makes them 20 times more effective than birth control pills, the patch, or the vaginal ring, according to the American College of Obstetricians and Gynecologists.
It’s not just the effectiveness that makes LARCs a solid choice for birth control. “It’s a onetime cost. They're long-acting. They have minimal side effects, for the most part,” says Kecia Gaither, M.D., ob-gyn, maternal fetal medicine specialist and director of perinatal services at NYC Health + Hospitals/Lincoln. “When you're looking at the big picture, those are some really nice things to consider.”
But what, exactly, are the different types of LARCs? How do they work? And how effective are they preventing pregnancy—especially when compared with other forms of birth control? We asked the experts to break it down.
Types of LARCs
There are two different types of long-active reversible contraceptives: intrauterine devices (better known as IUDs), which are inserted into the uterus, and the implant, a small rod-shaped device that is implanted under the skin of the upper arm.
In fact, there are two different types of IUDs—copper IUDs and hormonal IUDs. While they’re both extremely effective at preventing pregnancy, they work in completely different ways.
The copper IUD
The copper IUD is approved to work for the longest duration of time—10 years (though your gyno can remove it at any time if you want to start getting pregnant). It’s also completely nonhormonal. “It basically creates an inhospitable environment for pregnancy. The copper presence prevents the fusion of the egg and the sperm,” explains Shirazian. It’s a great option if you don’t want to get pregnant any time in the near (or distant!) future, or if you want a completely hormone-free method of birth control.
The hormonal IUD
The hormonal IUD prevents pregnancy through introducing the hormone progesterone—one of the two hormones typically used in the birth control pill—into your system. “What progesterone does from a contraceptive point of view is it thickens the cervical mucus, which makes it difficult for the sperm to even get through the cervix and into the uterus,” says Gaither. “The other thing that hormonal contraception devices do is inhibit ovulation,” she adds. “So you've got a two-hit wonder from using the hormonal IUD."
Hormonal IUDs are over 99% effective at preventing pregnancy and last between three and six years. (The length of effectiveness for hormonal IUDs depends on the brand.)
If an IUD doesn’t feel like the right fit for you, there’s another LARC option: the birth control implant.
The implant works much the same way as the hormonal IUD. Instead of being placed in the uterus, the implant is a small device about the size of a matchstick that’s placed in your upper arm just underneath the skin, explains Shirazian. Like the IUD, it secretes a form of progestin. “Progesterone has the same effect whether it's subdermal or in the uterus,” says Shirazian. “Progesterone is absorbed into the bloodstream, and the presence of progesterone basically has the same effect as the hormonal IUD would.”
The birth control implant is over 99% effective and can prevent pregnancy for up to three years.
LARCs vs. Other Types of Birth Control
LARCs are by no means the only form of effective birth control. But one of the major benefits to this type of contraceptive—and a huge factor in their effectiveness—is that once they’re inserted, there’s no room for human error.
“We have something called ‘typical use’ of contraceptive methods,” explains Shirazian. “If typical use requires someone to remember to take it, it's naturally going to be less effective in the population overall.”
If you take the birth control pill perfectly, for example—meaning you take it at the exact same time every single day and never miss a dose—it’s 99% effective at preventing pregnancy, according to Planned Parenthood. But most people aren’t perfect. Somewhere along the way, you may forget or miss a pill. With typical use, the pill is really only about 91% effective.
There’s a similar loss of effectiveness for the birth control ring (99% perfect use versus 91% typical use), diaphragms (94% perfect use versus 88% typical use), and other types of birth control. So, if you’re prone to falling in the “typical use” birth control trap, LARCs are a great way to get the maximum effectiveness—with no effort on your part required.
Are LARCs Right for You?
If a pregnancy isn’t in your five-year plan and the thought of missing a pill gives you anxiety, talk to your doctor to see if long-active reversible contraceptives are right for you.
Just remember: LARCs are extremely effective at preventing pregnancy, but not STIs—so be sure to always practice safe sex and use condoms.
Originally Appeared on Glamour