What Is Emergency Birth Control and How Does It Work?

For starters, you don’t want this to be your routine contraception.

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OK, so you were in the moment with your partner and you may have forgotten to use protection. After the feelings of passion faded, you were left with two things: Memories of a great time and … ugh, woops.

First of all, it happens, so don’t beat yourself up. Secondly, all is not lost—you still have options. Enter: Emergency contraception.

“Emergency birth control—which includes different kinds of pills and the copper IUD—helps prevent pregnancy for up to five days after unprotected sex,” says Kecia Gaither, MD, director of perinatal services at Lincoln Medical and Mental Health Center.

While emergency birth control is a safe and effective contraceptive method, it’s also important to remember that it does *not* protect against STDs, says Dr. Gaither. (For STD protection, condoms are the way to go.) Learn more common myths about birth control.

Here are other important facts to know about emergency birth control:

FACT: There are two main kinds of emergency contraception pills.

Emergency birth control (EBC) may be known as the “morning-after pill,” but depending on the pill, it can prevent pregnancy three or even five days after unprotected sex.

EBC with progestin: This kind of emergency birth control contains the hormone progestin, one of the hormones in regular birth control pills. “It can lower your chances of getting pregnant by 75 to 89 percent if you take it within three days after unprotected sex,” says Dr. Gaither. It’s available over the counter for all women of all ages.

EBC with ulipristal acetate: The other kind contains a medication called ulipristal acetate, which works differently to delay ovulation. It lowers your chances of getting pregnant by 85 percent if taken within five days of unprotected sex. It’s available only by prescription. “It’s more effective than other EC pills because its efficiency doesn’t decline the longer you wait to take it,” says Dr. Gaither.

If you’re past that three- or five-day window, depending on the emergency birth control that you chose, call your doctor or pharmacist to ask about your best options.

FACT: You might get your next period late.

If you get a period, it can be troubling when it’s late or you skip a month. There are many reasons your period is suddenly MIA, but if you just took emergency birth control, there’s a good chance that’s the reason.

“You might freak out thinking that you’re pregnant, but this is totally normal,” says Dr. Gaither. “And your period could be really heavy.” Here are some other reasons your period may be heavier than normal

FACT: You shouldn’t use emergency contraception as your go-to birth control method.

It may be tempting to forgo the daily birth control pill for one that works on an as-needed basis, but Dr. Gaither doesn’t recommend it. “For starters, it’s not as reliable as routine birth control,” she says. “And it’s more expensive and may have more side effects.”

Some routine birth control options to consider:

FACT: Nausea is a very common side effect of morning-after pills.

Nausea is no fun in any circumstance, but after taking emergency birth control, it’s normal. Fatigue, headaches, dizziness, breast tenderness, and cramps are other common side effects.

What’s important to remember, though, is if that nausea turns into vomiting soon after you take your emergency birth control, it won’t work. “If you throw up within two hours of taking the pill, it won’t be effective and you’ll have to take it again,” says Dr. Gaither.

If you’re sexually active and not trying to get pregnant, it’s wise to talk to your doctor about a routine birth control method. Not only is it more reliable, but you’ll save yourself the worry and stress of another “woops” moment.