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Home > Be Healthy > Health Library > Emergency Contraception
Emergency contraception is a way to prevent pregnancy if:
If you had sex without birth control, there is a chance that you could get pregnant. This is true even if you have not started having periods yet or you are getting close to menopause. You could also get pregnant if you used a birth control method that is not very reliable or if you didn't use it the right way.
Using emergency contraception right away can prevent an unwanted pregnancy and keep you from worrying while you wait for your next period to start.
There are two main types of emergency contraception: pills and the copper intrauterine device (IUD). Most women choose pills because they work well, don't cost a lot, and are usually easy to get. The IUD works very well, but it has to be inserted by a doctor.
Emergency contraception pills work by preventing ovulation.
Emergency contraception hormones may prevent fertilization by stopping the ovary from releasing an egg (ovum). They also make the fallopian tubes less likely to move an egg toward the uterus. Emergency contraception is also thought to thin the lining of the uterus, or endometrium. The thickened endometrium is where a fertilized egg would normally implant and grow.
The copper IUD for emergency contraception may prevent fertilization or implantation.
Emergency contraception. You can get emergency contraception without a prescription at most drugstores.
Some types of emergency contraception, such as ulipristal acetate (for example, ella) are available only with a prescription from a doctor.
Birth control pills. If you already have birth control pills on hand, you may be able to use them for emergency birth control. To find out which brands of pills work and how to take them, go to www.plannedparenthood.org or https://ec.princeton.edu for emergency contraception information.
Some pharmacists will not sell emergency contraception or fill prescriptions for birth control pills. If this happens to you, ask for the location of a pharmacist who will, or go to or call the Planned Parenthood clinic nearest you.
IUD. You can get an IUD from many doctors, from college and public health clinics, or in most hospital emergency rooms. An IUD has to be inserted by a doctor or other health professional.
Emergency contraception pills
The pills come in 1-pill or 2-pill packages. Follow the directions in the package or take them as your doctor directs you to.
You can take emergency contraception up to 5 days after unprotected sex.
Birth control pills as emergency contraception
For most regular birth control pills, you take one dose of 2 to 5 pills as soon as you can. Then you take a second dose 12 hours later. The dose depends on the type of pill.
If you use birth control pills for emergency contraception, keep the following in mind:
A doctor or other health professional has to insert an IUD.
The sooner you use emergency contraception, the more likely it is to prevent pregnancy. Overall:
If you are overweight or obese, emergency contraception pills may not work as well to prevent a pregnancy. Talk with your doctor about methods that aren't affected by your weight, such as the copper IUD.
If you haven't started your period within 3 weeks after using emergency contraception, get a pregnancy test.
Emergency contraception may cause some side effects.
Call your doctor if you have a headache, dizziness, or belly pain that is severe or that lasts longer than 1 week.
If you are already pregnant, most pills won't harm the fetus. But some pills, such as ulipristal, may cause problems with the pregnancy. More research is needed to know for sure. An IUD could cause problems with the pregnancy.
Other Works Consulted
Stewart F, et al. (2007). Emergency contraception. In RA Hatcher et al., eds., Contraceptive Technology, 19th ed., pp. 87–112. New York: Ardent Media.
Current as of:
October 8, 2020
Author: Healthwise StaffMedical Review: Sarah Marshall MD - Family MedicineKathleen Romito MD - Family MedicineAdam Husney MD - Family MedicineElizabeth T. Russo MD - Internal MedicineRSURemoved
Current as of: October 8, 2020
Author: Healthwise Staff
Medical Review:Sarah Marshall MD - Family Medicine & Kathleen Romito MD - Family Medicine & Adam Husney MD - Family Medicine & Elizabeth T. Russo MD - Internal Medicine & RSURemoved
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