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Birth control implants: The incredibly effective contraception that you've never heard of

Birth control control implants are, hands down, the most effective, non-permanent contraceptive.

The 4-centimeter device, inserted by a doctor into the arm, is far more effective than birth control pills and condoms at preventing pregnancy — and even slightly better than other long-term contraceptives, such as IUDs. Federal data shows that 0.05% of implant users become pregnant in a given year, compared to 0.2% of hormonal IUD users and 9% percent of women on birth control pills.

Birth control implants are also, hands down, the least popular contraceptive. Fewer women rely on the device than any other method. There are ten times as many women using IUDs as there are with the implant.

contraceptive choices

These two facts, taken together, are a bit odd. Birth control implants both work the best — but are used the least, and don't get talked about too much as a contraceptive option. The devices are a relatively new form of birth control and insertion requires special training on the part of a gynecologist.

"IUDs have been around a whole lot longer than implants, that's a huge factor," says Jill Rabin, a professor of obstetrics and gynecology at Hofstra North Shore-LIJ School of Medicine. "They're what doctors are used to, and recommend. Then there's also the fact that ob-gyns aren't trained to operate on arms, even though it's not difficult to do. It's an easy insertion, but also different from our typical work."

Rabin inserts both IUDs and implants regularly at her practice in Long Island. And I got to talk to her this week about birth control implants: how they work, what kind of side effects they have, and why so few women use them.

1) Birth control implants prevent pregnancy by delivering hormones to the blood stream


A birth control implant (the rod to the left of the bone) in its natural habitat, the arm (British Medical Journal)

Gynecologists typically use a birth control implant called Nexplanon, which is manufactured by pharmaceutical company Merck. Some also will use an older version of the implant called Implanon, the main difference between the two is that Nexplanon (a newer implant) is manufactured to show up in x-rays. Implanon isn't.

Both of the implants contain 68 milligrams of etonogestrel that slowly get released during the device's three-year lifespan. This is actually the same hormone used in other contraceptives like Nuvaring, a contraceptive ring inserted into the vagina.

The etonogesterel hormone makes the uterus a really sad, difficult place for a sperm to even get to — or, if a sperm does make it there, for it to fertilize an egg and create an embryo.

"Because of the etonogesterel the cervical mucus gets thick and the lining of the uterus gets thin, which makes a fertilized egg not excited about implanting there," Rabin says ."Think about if you were a fertilized seed pod and you were looking for a place to settle to grow into a plant."

Landing in the uterus of an implant user is akin, as Rabin puts it, "to landing on a rock rather than soil."

2) Birth control implants take a few minutes to insert with a needle

The Nexplanon applicator (British Medical Journal)

The insertion process works like this: a gynecologist or other provider will measure eight centimeters up from the elbow and make a mark between the bicep and tricep muscles. That's where they'll poke a needle under the skin to insert the implant. They'll also make another mark four centimeters further up the arm, closer to the shoulder, which is where the implant should stop once inserted.

"We clean the arm, and then numb it with lidocaine [an anesthetic]," Rabin says. "We put the tip of the needle in at the first mark at an angle, to tent up the skin. And then we basically use the inserted needle to deploy the device. Once you remove the needle, you have the applicator out and the implant under the skin."

Rabin checks the applicator afterwards to make sure that the implant is no longer there, and also the patient's arm, to ensure she can feel the device under the skin. Typically she can but, if not, "we use an ultrasound to check. Almost 100 percent of the time it's right where we put it."

Because of the anesthetic, the insertion process shouldn't hurt. Merck does warn that insertion and removal of the implant do have the possible side effects of "pain, irritation, swelling, bruising, scarring" and other risks. And if you spend any time poking around on Google, you'll find images of women who show big bruise marks after implantation.

There isn't a ton of research on this yet, but the studies that do exist suggest this is an atypical reaction. One 2012 study of 23 women receiving the birth control implant showed that 61% experienced minor discomfort at the insertion site that disappeared within a week. Doctors will typically put a pressure bandage over the insertion site, left there for a day or two after, to minimize the risk of a bruise.

3) Patients should be able to feel (and maybe even see) the implant under their skin

"You should definitely be able to feel it if you poke at your arm," Rabin says. "Whether you can see the outline depends in part on your weight. Generally, if you're heavier with more fat tissue, you might not see it."

I asked Rabin whether she thought this was a barrier to some women using the implant — did the idea of seeing the outline of a tiny, rod inside their arm weird patients out? She says no.

"I really think that's minor," Rabin says. "The biggest barrier is having a provider who is trained, on board, and willing to take the time to do the procedure."

That being said, it is still possible that one reason women don't ask about the birth control implant in the first place is because they're not quite ready to see the outline of a foreign object in the side of their arm.

4) The most common side effect of the implant is irregular bleeding

Much more so than other contraceptives, the birth control implant causes high rates of irregular bleeding.

The best data available about half of women using the implant will have infrequent bleeding, or no periods altogether. Another 20 percent or so will have heavy bleeding or irregular bleeding, more so than they did prior to the implant's insertion.

Nobody know why, exactly, this happens at such high levels with the implant. "The mechanism of irregular cycles of bleeding are complex and poorly understood and few studies have been conducted on the management of bleeding with the implant," the Association of Reproductive Health Professionals writes.

Of the women who discontinue implant use, the most common reason is irregular bleeding. This isn't to say, however, that all women with irregular bleeding decide to have their implant taken out. Instead, it's actually a relatively small minority.

"About one in ten women who have irregular bleeding want the device removed," Rabin says. "It's a trade-off that most women think is worth it for the contraceptive's efficacy."

5) Complexity, newness of the product, and training are obstacles of the implant

I ended my interview with Rabin circling back to my initial question: if the implant works so well, why do so few women use it? She homed in on three main obstacles:

  • The implant is relatively new. Implanon came onto the market in the United States in 1998, followed by Nexplanon in 2011. Birth control pills and even IUDs have been around significantly longer (the non-hormonal IUD Paragard, for example, came onto the market in 1988.) "It can be a matter of habit to rely on the device that you know," Rabin says. "But I think maybe a decade or so from now, you'll see more of an equalization between IUDs and implants."
  • The implant goes in the arm. Most of gynecologists' work happens, unsurprisingly, in women's reproductive organs. And while learning how to insert the implant is pretty easy (and taught in gynecology residencies) it does require doctors to work on a different part of the body than their day-to-day work typically requires.
  • Inserting an implant takes time. Sending a patient off with a prescription for birth control pills is the easier option for health care providers. They don't have to do anything else. But an implant (and an IUD) typically mean a follow-up appointment and a bigger time commitment to insert the device. Separate research has shown that women's health providers are sometimes hesitant to take the extra time that more effective contraceptives require. "It takes more time than the pill, its a procedure but it does give you better contraceptive coverage," Rabin says.