Emergency contraception is a method of preventing pregnancy after unprotected sexual intercourse. It's for emergency use and should not be relied upon as a regular method of birth control.
Emergency contraception is most effective if used as soon as possible after unprotected sex. For people at least 17 years old, emergency contraception can be purchased over-the-counter, without a prescription.
How Does it Work?
You take fairly high doses of progestin – a synthetic form of the hormone progesterone – with or without the hormone estrogen (which are the hormones used in birth control pills).
If taken within 72 hours (three days) of unprotected sex, the hormones have a high success rate at preventing ovulation or implantation of a fertilized egg in the lining of the uterus. However, even if taken less than 24 hours after unprotected sex, the highest success rate is 89 percent.
How is it Used?
There are two effective ways to use emergency contraception. In the first method, a female takes two prescribed progestin tablets alone.
In the second, the female takes hormone pills (either progestin alone or a progestin-estrogen combination) once, and then again 12 hours later. A medical provider will tell you which is correct for you.
When Should it be Used?
Emergency contraception is no substitute for good, before-the-fact birth control. Talk with your healthcare provider about preventing pregnancy and sexually transmitted infections (STIs) before the issues arise. You would use this method only in an emergency, such as:
- You were forced to have sex without protection.
- You had sex without using any kind of birth control protection and do not desire pregnancy.
- You used a condom or other barrier method but it broke.
- You missed more than two birth control pills and didn't use a condom.
Side Effects
Common side effects include nausea and occasionally vomiting (an anti-nausea drug is sometimes prescribed for this). If pregnancy does occur despite using the emergency pills, there is no increased risk of birth defects.
You should not use emergency contraception if you're already pregnant, know you are sensitive or allergic to the medication, or have been having abnormal vaginal bleeding.
Does it Protect Against STIs?
STI stands for sexually transmitted infection. STI risk varies depending on how you choose to protect yourself and your partner during sexual or intimate activities.
Unfortunately, emergency contraception does not protect against STIs.
Things to Remember
For emergency contraception, don’t just take whatever birth control pills you might have around the house or get from friends. The proper number of pills to take depends on which type of pill you use. Check with a medical provider to find out what number of pills is right for you.
This method is not approved for use when taken more than three days after unprotected sex. Call your healthcare provider to discuss your options after this three-day interval has passed.
Some emergency contraception products are available over-the-counter at drugstores, without a prescription; others can be distributed by pharmacists, without a prescription from a medical provider.
Emergency contraception does not cause an abortion. Emergency contraception works by preventing a pregnancy from occurring, not by terminating a pregnancy. Often you will have bleeding after taking the medication, as with a period.
Last Reviewed: January 2019
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