
Whether you got carried away in the moment, forgot to take your birth control pills, or the condom broke, accidents — and unprotected sex — do happen, which might explain why roughly one in nine U.S. women has used emergency contraception. This fact also highlights why access to EC is so important. Thankfully, as of 2013, you can purchase levonorgestrel-containing EC pills, like Plan B One-Step, without a prescription. That means you can buy EC at your local drugstore, whenever you need it — no frantic, last-minute calls to your doctor necessary.
Unfortunately, confusion over how emergency contraception prevents pregnancy — and the risks associated with it — has led to a lot of misinformation. To clear up the rumors, we asked experts to answer six of the most common questions about EC.

The most common forms of emergency contraception come as pills and prevent pregnancy by stopping your body from releasing an egg. “Releasing an egg requires a surge of estrogen,” says Valerie French, MD, M.A.S., an Ob/Gyn and fellow in family planning at the University of California San Francisco. EC pills contain progestin to override that estrogen and delay ovulation. In rarer cases, they may also inhibit the fertilization of an egg or implantation to the uterus. However, EC is not effective after implantation has occurred and will not cause a miscarriage.

The sooner the better: When taken in the first 24 hours after unprotected sex, EC pills can be up to 95% effective. That said, it’s not a lost cause if you let a couple of days slip by before taking action.
Can’t get to the store, much less the doctor? Send your partner to pick up EC for you. “A lot of people don’t realize that men can buy it, too,” says Dr. French. Or, you could keep EC in your medicine cabinet — just in case you ever need it.

“In the old days, doctors had women take a massive dose of [a synthetic estrogen called] DES (a.k.a. Diethylstilbestrol) for five days,” says Mary Jane Minkin, MD, a clinical professor of obstetrics and gynecology at Yale University School of Medicine. Women didn’t get pregnant (though the method wasn’t 100% effective) after taking the pills, but they did become sick with severe nausea and headaches.
“Emergency contraceptive pills have gone through many evolutions in the past 40 years and now only contain a synthetic progestin (Levonorgestrel) — no estrogen, making the side effects less common,” says Dr. Minkin. “You may experience a little disruption in your menstrual cycle that month from taking the bigger dose of progestin, and some women experience mild nausea, cramping, or moodiness, but generally speaking, most tolerate it pretty well.”
Any side effects you do experience should go away within a couple of days. In the rare case you do feel queasy and throw up within a few hours of taking your emergency contraception, contact your healthcare provider. “You may need to take another dose if your body didn’t have time to absorb the medication,” says Dr. French.

There is no evidence that using emergency contraception today will have a negative impact on your ability to get pregnant later. “The hormones in emergency contraception will be out of your system after a couple of days,” says Dr. Minkin. “And it will not have a long-term effect on ovulation.” This is why even after EC does its job, you’re once again at risk for getting pregnant.
What can affect your future fertility? For one, sexually transmitted infections from unprotected sex — so get tested with your partner and stock up on condoms.

"Emergency contraception is contraception — a way to prevent conception. It cannot stop a pregnancy that has already occurred," says Vanessa Cullins, MD, an Ob/Gyn and vice president for external medical affairs at Planned Parenthood. "These methods work by delaying ovulation or preventing sperm from entering the uterus, not the removal or displacement of an existing pregnancy."

There is no limit to the number of times you can use emergency contraception. “While the dose of synthetic progestin is higher than what you’d get with your normal birth control, it’s still a safe level — even women who can’t take regular birth-control pills because of high blood pressure or blood clots can safely take emergency contraceptive pills, because they don’t contain estrogen,” says Anne Burke, MD, M.P.H., associate professor of gynecology and obstetrics at Johns Hopkins Medicine in Baltimore. “EC is a short, one-term dose that is cleared by your system and has no lasting health effects.”
But while EC is a great safety net, you may want to reexamine your method of birth control if you find yourself needing it on a frequent basis. In addition to not protecting you against sexually transmitted infections, EC can be more costly and, depending on when it’s taken, less effective than traditional methods of birth control. “If someone continually needs EC, I’d like to talk to her about what’s going on,” says gynecologist Colleen Krajewski, MD, M.P.H. “It’s okay if you don’t like taking birth-control pills. There are other methods out there — hormonal and non-hormonal — that are close to 100% effective.”
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