Emergency Contraception


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What is emergency contraception?

Emergency contraception is a form of birth control. It can be used to prevent pregnancy if you have had unprotected sex or if you used a birth control method that failed. For example, you might use emergency contraception if:

  • You were not using any type of birth control when you had sex
  • You forgot to take your birth control pills
  • Your partner's condom broke or slipped off during sex
  • Your diaphragm slipped out of place during sex
  • You were forced to have unprotected sex

Emergency contraception does not protect against sexually transmitted infections (STIs).

What types of emergency contraception are available?

Two types of emergency contraception are available: emergency contraceptive pills and the copper-containing intrauterine device (IUD).

Emergency contraceptive pills include the following:

  • A pill that contains levonorgestrel (some brand names: My Way, Next Choice, Plan B One-Step). This is most effective if it is taken within 72 hours after unprotected sex. It can reduce the risk of pregnancy for up to 120 hours (5 days), but it is less effective as time passes.

Most brands only require a single dose of 1 pill. Some brands have 2 doses (1 pill followed by a second pill 12 hours later). Studies have shown that the 2 doses may also be taken together. In the United States, this type of emergency contraceptive pill does not require a prescription from your doctor. It is available over the counter to women and men of any age at many pharmacies.

  • A pill that contains ulipristal acetate (brand name: Ella). This is taken as a single dose of 1 pill within 120 hours (5 days) after unprotected sex. This type of emergency contraceptive pill requires a prescription from your doctor.

The U.S. Food and Drug Administration (FDA) says that some brands of regular birth control pills can be used in increased doses for emergency contraception. However, this method is less effective. It tends to cause more side effects. To find out whether your brand of regular birth control pills is safe for emergency use, talk to your doctor.

The copper-containing IUD (brand name: Paragard) is a small, T-shaped device that is placed inside the uterus by your doctor. To be used for emergency contraception, the IUD should be placed within 5 days after unprotected sex. The IUD can be left in your body for up to 10 years to prevent pregnancy. Some women use IUDs as their regular form of birth control.

How do emergency contraceptive pills work?

Pills used for emergency contraception may prevent pregnancy by:

  • Preventing ovulation (release of an egg from the ovaries)
  • Preventing an egg from being fertilized by sperm
  • Preventing a fertilized egg from attaching itself to the wall of the uterus

Emergency contraceptive pills are not the same as mifepristone (brand name: Mifeprex), which is the medicine known as the "abortion pill." This medicine is taken in the early weeks of pregnancy to end the pregnancy. Pills used for emergency contraception cannot end a pregnancy once a fertilized egg has attached itself to the wall of the uterus.

Emergency contraceptive pills are sometimes called the “morning after pill.” However, these medicines should be taken as soon as possible after you have unprotected sex if you want to prevent pregnancy.

How does the copper-containing IUD work?

Unlike emergency contraceptive pills, the IUD doesn't stop your ovaries from releasing an egg. The IUD can prevent an egg from being fertilized, or it can stop a fertilized egg from attaching itself to the wall of the uterus.

How effective are emergency contraceptive pills?

Emergency contraceptive pills can be very effective if they are used in time. The sooner you use this type of emergency contraception after unprotected sex, the more effective it is. In general, the pill that contains ulipristal acetate reduces the risk of pregnancy more effectively than pills that contain levonorgestrel.

It is important to remember that emergency contraceptive pills will not prevent pregnancy if you have unprotected sex after taking them.

Does being overweight or obese decrease the effectiveness of emergency contraceptive pills?

Yes. Evidence has shown that being overweight or obese can decrease the effectiveness of emergency contraceptive pills.  

If you have a body mass index (BMI) between 25 and 30 (which is considered overweight), pills that contain levonorgestrel may be less effective. The pill that contains ulipristal acetate is still effective up to a BMI of 35.

Women who are overweight or obese and need emergency contraception should consider using the copper-containing IUD. It is the most effective option for women of any weight. If you are unable to get the copper IUD, take whichever type of emergency contraceptive pill is available.

How effective is the copper-containing IUD for emergency contraception?

This type of IUD is very effective for emergency contraception. It can reduce your risk of pregnancy by more than 99% if it is inserted within 5 days after unprotected sex.

Does using emergency contraception cause any side effects?

Some women feel sick to their stomach after they take emergency contraceptive pills. This feeling should go away in about 2 days. Your doctor can give you medicine that may help you feel better. Other possible side effects include headache, breast tenderness, changes in your period, and abdominal pain.

The most common side effects of the copper-containing IUD are heavier, longer periods and spotting between periods. Most side effects will get better in about 2 to 3 months.

Who should not use emergency contraception?

If you know you are pregnant, you should not use emergency contraceptive pills. It is also recommended that women who are breastfeeding should not use the pill that contains ulipristal acetate.

You shouldn't use the copper-containing IUD if:

  • You know you are pregnant
  • You have abnormal bleeding
  • You have cancer of the cervix or uterus
  • You are allergic to copper

When do I need to start using my regular birth control again?

The copper-containing IUD can be used as your regular form of birth control. It can be left in your body for up to 10 years to prevent pregnancy.

After you take emergency contraceptive pills, your period may come earlier or later than usual. Talk to your doctor if you do not get your period within 1 month after taking the pills.

If your regular form of birth control is a barrier method (for example, condoms or a diaphragm), you may go back to using it right away after taking emergency contraceptive pills.

If your regular form of birth control is a hormonal method (for example, birth control pills, hormone shots, the patch, or the vaginal ring), talk to your doctor about when you should start using it again.

Where can I get emergency contraception?

In the United States, emergency contraceptive pills that contain levonorgestrel do not require a prescription from your doctor. They are available over the counter to women and men of any age at many pharmacies. The emergency contraceptive pill that contains ulipristal acetate requires a prescription from a doctor. You must go to a doctor to have a copper-containing IUD inserted.

Other places to get emergency contraception include university and women's health centers, health departments, Planned Parenthood centers, and hospital emergency departments.

Written by familydoctor.org editorial staff

Reviewed/Updated: 01/15
Created: 10/04

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