by  Carrie Macmillan, Yale University

Credit: CC0 Public Domain

When it comes to birth control, many preconceived notions may influence which method a woman chooses.

Whether it's the belief that some forms bring weight gain, cause cancer, or affect future fertility, there's considerable misinformation about birth control—which 99 percent of sexually active American women report having used.

"Considering the high number of women who use birth control at some point in their life, clearing up myths is incredibly important," says Nancy Stanwood, MD, MPH, chief of Yale Medicine Family Planning. "Women deserve great medical care for this aspect of their health. As medical providers, we welcome conversations with patients about contraception. We want to educate and empower them. We are here to find out each woman's needs and help connect her with the method that is best for her."

Often, that conversation includes education. Below, Yale Medicine experts answer common questions women have about contraception.

Which birth control works best?

"People often have a misconception that all birth control methods are the same in terms of protection. But that's not true. Some work better than others," Dr. Stanwood says. "I tell patients that, aside from permanent sterilization (tubal ligation for women, vasectomy for men), what gives the most protection is an intrauterine device (IUD) or the arm implant, both of which have a less than 1% risk of pregnancy in a year."

An IUD is a small, soft, flexible piece of plastic shaped like a "T"—it is inserted into your uterus, via your cervix, by your doctor. There are several brands (Liletta, Kyleena, Mirena, Skyla), all of which release the hormone progestin, which changes the cervix and uterus to prevent sperm from getting through to an egg. These hormonal IUDs protect against pregnancy for three to seven years, depending on which one a woman chooses. Another type of IUD (Paragard) is hormone-free and instead uses a copper coil, which also changes the cervix and uterus to prevent sperm from getting through to an egg, and it can be used for up to 12 years.

The arm implant, sold under the brand Nexplanon, is a rod about the size of a matchstick that is inserted under the skin of your upper, inner arm. It releases progestin and prevents pregnancy for up to five years by stopping ovulation and thickening cervical mucus.

The more commonly used contraception methods, including birth control pills, injections, arm patches, and vaginal rings have failure rates of about 10% in a year, Dr. Stanwood notes, noting that the problem isn't with the method but how it's used. "We're not perfect. We're human, and those methods require us to remember things. For people with hectic lives, those methods might not be ideal," she says.

Can birth control cause weight gain?

"Patients often tell me that they think all birth control causes weight gain, but there is only one method, the progestin hormonal injection given every three months, that is linked to weight gain," Dr. Stanwood says. "That's not to say women aren't gaining weight. Most American women naturally gain about 2 pounds every year, but it's not the pill or intrauterine devices causing it."

Sold under the brand name Depo-Provera, the birth control injection contains progestin and suppresses ovulation so that you don't release an egg each month and therefore can't get pregnant. One study showed that, over one year, women who used Depo-Provera gained five pounds more than those using a copper IUD. The reason Depo-Provera can cause weight gain, Dr. Stanwood explains, is that it can activate signals in the brain that control hunger.

Can birth control make you infertile?

Some women mistakenly believe that being on contraception will make it difficult for them to get pregnant once they stop, especially when they are using what's known as long-acting reversible contraception (LARC), such as IUDs or the arm implant.

These devices only interfere with conception when they are in place. "You could have an IUD or arm implant in for two years or even just a month, and if you don't like it, or you want to get pregnant, we take it out. It does not affect your future fertility," says Aileen Gariepy, MD, MPH, a Yale Medicine obstetrician-gynecologist. "Just because you choose a method that lasts for five, seven, or more years does not mean you have to have it in all of those years. That is just the amount of time it offers protection."

Is getting an IUD painful?

Some women worry that IUD insertion is painful; Dr. Stanwood says the experience varies for each woman. "For most, it's similar to a typical pelvic exam with a Pap test, but with a little more of a cramp," she says. "For others, I'm all done and they ask, "That's it? I didn't feel anything." Yet other women might feel more crampy. For most, it's a procedure that takes about five minutes total—with a few minutes of cramps that are worth it in exchange for many years of birth control."

IUD insertion is performed during a standard office visit. "Some spotting is expected after and might last the rest of the day," Dr. Stanwood says. Women who've recently given birth have a particularly easy time with the experience, she notes. "I like to let women who have recently delivered a baby know that they will have the least amount of discomfort in terms of insertion if they do it within a couple of months of having their baby, because the cervix tends to be open and the uterus isn't as bothered by it."

Dr. Stanwood jokes that, in general, it takes longer to talk to women about IUDs than it does to insert them.

Does the arm implant hurt?

Likewise, the arm implant is a quick and easy procedure. Your medical provider will apply a local anesthetic to numb your arm and use a special device to slide the implant under your skin. "We slip it through a little hole on the inside part of the arm and it rests under the skin," Dr. Stanwood says. "It's kind of like getting blood drawn or getting an IV put in. Getting it removed is similarly very quick. Plus, it's very discreet. A woman can feel it if she pushes on it, but it's not sticking out."

What birth control is best for teenagers?

IUDs and contraceptive implants can be used by all women of childbearing age, including teens. In fact, the American Academy of Pediatrics recommends that IUDs and the arm implant should be the first-line choice for young women who are sexually active.

"If a parent of a teen is wondering what might be safe for his or her daughter to consider, the arm implant and the IUD can serve teens the best," Dr. Stanwood says. "That's because you set it and forget it. They are busy. This allows them to focus on academics."

Is birth control safe?

While some forms of birth control carry health risks, it's important to note that, in fact, a higher number of serious complications are associated with pregnancy and childbirth, doctors say.

Combined hormonal birth control (the pill, the patch, and the ring, which all contain the hormones progestin and estrogen) is associated with a small increased risk of blood clot, stroke, and heart attack. These risks are higher among women who smoke and are over age 35, or who have multiple cardiovascular disease risk factors.

"With using hormones to prevent pregnancy, one of the things we worry about is that they increase a woman's risk of forming a clot that can travel to any place in the body. If you are not taking any kind of contraception and you're not pregnant, you are at your lowest risk of having a clot," Dr. Gariepy explains. "The next highest risk is contraception that uses estrogen or progestin; these are the most common forms of birth control pills. And then the next highest risk is being pregnant. So, when we talk about safety, we always want to ask, "Compared to what?" In this case, your risk of forming a clot while on the birth control pill is lower than it is when you are pregnant."

Meanwhile, some of the side effects associated with combined hormonal birth control methods are actually beneficial to some women. For example, they can make periods lighter, shorter, and more regular. Birth control pills can also reduce acne and the frequency of migraines associated with menstruation. Plus, the pill decreases a woman's risk of uterine, ovarian, and colon cancer.

Is it OK to not get your period on birth control?

Certain forms of contraception make a woman's periods less frequent or very light—or eliminate them altogether. This is completely safe, says Amanda Lendler, MSN, CNM, a Yale certified nurse-midwife.

During a woman's monthly menstruation cycle, her uterus creates a lining to prepare for pregnancy. "Hormonal birth control may decrease the lining built up during a menstrual cycle, leaving little or no uterine lining to shed each month," Lendler explains. "That means there is little or nothing to bleed each month, and there's no harm in that."

At the end of the day, Lendler and her colleagues urge women to talk to their provider about any questions they may have about contraception.

"Birth control is not one-size-fits-all," Dr. Stanwood says. "We focus on what each patient wants and share our expertise to help her find what is best for her."

Provided by Yale University