What Is It?

Emergency contraception is a way to prevent pregnancy after unprotected sex. Often called the morning-after pill, emergency contraceptive pills (ECPs) are hormone pills that can be taken up to 72 hours after having unprotected sex.

Most states require a doctor to prescribe emergency contraception; however, recently some states have allowed nonphysicians to provide ECPs. Either way it is important to seek medical help and guidance.

Emergency contraception is most effective when it is taken as soon as possible after intercourse. But some studies have shown that it can still work up to 120 hours after intercourse.

The intrauterine device (IUD) can sometimes be used as a form of emergency contraception. This is rarely prescribed for teens, though.

How Does It Work?

In high doses, the hormones estrogen and progesterone can prevent pregnancy. The number of pills taken depends on the type of pill being used. The first dose of pills should be taken within 72 hours of unprotected intercourse followed by a second dose of pills 12 hours later.

The hormones may work in a number of ways to prevent pregnancy. They may delay ovulation (the release of an egg during a girl's monthly cycle), affect the movement and function of the sperm, affect the development of the uterine lining, and disrupt the actual fertilization process.

ECPs are less effective if fertilization has already occurred. If implantation has already occurred and a girl is pregnant, ECPs will not interrupt the pregnancy.

How Well Does It Work?

About 1 or 2 in every 100 women who use ECPs will become pregnant despite taking ECPs within 72 hours after having unprotected sex. The effectiveness of emergency contraception methods is calculated differently from the effectiveness of other contraceptives because of how they are used. Emergency contraception is the only type of contraception method that is used after unprotected sex.

Emergency contraception is most effective when taken as soon as possible after unprotected sex. Because of this, the name morning-after pill is somewhat misleading: Ideally the pill should be taken immediately after sex, without waiting for the next morning.

Emergency contraception will not prevent pregnancy if a girl has unprotected sex after taking the ECPs.

Because emergency contraception does not prevent all pregnancies, a woman should see her doctor if she doesn't get her next expected period after taking it.

Protection Against STDs

Emergency contraception does not protect against sexually transmitted diseases (STDs). Couples having sex must always use condoms to protect against STDs even when using another method of birth control.

Abstinence (not having sex) is the only method that always prevents pregnancy and STDs. If a girl has been forced to have unwanted sex, she should see a doctor right away to be tested for STDs. That's because it's important to treat some STDs immediately before they develop into bigger problems.

Possible Side Effects

The larger-than-normal dose of hormone causes some side effects in many of the women receiving emergency contraception pills. These side effects include nausea, vomiting, breast tenderness, and headache. Such side effects are usually minor, and most improve within 1 to 2 days. A girl's menstrual period may be temporarily irregular after taking ECPs.

Who Uses It?

Emergency contraception is not recommended as a regular birth control method. Instead, it is used for emergencies only. If a couple is having sex and the condom breaks or slips off, if a diaphragm or cervical cap slips out of place, or if a girl forgot to take her birth control pills for 2 days in a row, a girl may want to consider using emergency contraception. It is also available to teens who are forced to have unprotected sex.

Emergency contraception is not recommended for girls who know they are pregnant.

How Do You Get It?

In most cases, a doctor must prescribe ECPs. Many health clinics also provide them. You must go as soon as possible after having unprotected sex. The Association of Reproductive Health Professionals keeps a list of providers who prescribe emergency contraception. You can find the name of someone in your area by calling their hotline at (888) NOT 2 LATE.

How Much Does It Cost?

Depending on the types of pills that are prescribed, the emergency contraceptive pill costs between $8 and $35. Many health insurance plans cover the cost of emergency contraception and family planning clinics (such as Planned Parenthood) may charge much less.

Reviewed by: Larissa Hirsch, MD
Date reviewed: February 2007
Originally reviewed by: Neil Izenberg, MD, and George A. Macones, MD