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When used correctly, emergency contraception works well to prevent pregnancy after unprotected sex. It can be useful if birth control fails (like when a condom breaks or slips off), if birth control wasn’t used during sex, or after sexual assault or rape. But there’s a fairly short time in which to use it. That means you often need quick answers.

I get many calls and messages from patients with questions about emergency contraception, or EC. Here are the five questions I’m asked most often.

1. How quickly after unprotected sex do I have to use EC?

This is usually the first thing my patients want to know. The answer depends on which EC option they choose.

The most effective EC option is a copper IUD (intrauterine device). An ob-gyn can place this device in the uterus within 5 days after unprotected sex. I tell my patients they can expect 5 to 10 minutes of strong cramping and discomfort at the time of placement. Then you can leave in the IUD for ongoing birth control.

The other options are known as morning-after pills. Some pills need a prescription from your ob-gyn or a health care professional. Others can be bought without a prescription. These are the two types of pills I recommend:

  • Ulipristal pills. These require a prescription. They can be used up to 5 days after unprotected sex.

  • Over-the-counter progestin-only pills. Most pharmacies carry these pills. I suggest calling ahead to be sure they are in stock. You should use progestin-only pills within 72 hours, or 3 days, after unprotected sex.

Some research suggests that morning-after pills may be less effective if you are overweight or obese. Copper IUDs are not affected by your weight.

If it’s been longer than 5 days since you’ve had unprotected sex, you should plan to take a pregnancy test. You can see a health care professional for a pregnancy test or do one at home. Home tests are most accurate when your period is at least 1 week late. Schedule a health care visit if you do an at-home test and it’s positive.

Note that if you are already pregnant, EC cannot end your pregnancy. EC only prevents pregnancy from occurring. It does not cause an abortion.

2. How soon will I get my period after using EC?

With all methods of EC, you usually get your period within 1 week of the expected time. That means anytime from a week before it’s expected to a week afterward. You may have irregular bleeding or spotting. This is normal.

See a health care professional if you’ve used EC and your period is more than a week late. There is a small risk that EC may not work, so this may be a sign you are pregnant.

3. Is it safe to use EC more than once during a single menstrual cycle?

Yes, it’s safe to use morning-after pills (both progestin-only pills and ulipristal pills) multiple times in one menstrual cycle.

But frequent use of these pills isn’t the best birth control plan. For one, it will probably cost more than planned birth control. And you may not always have enough time to find and get to a pharmacy that has pills in stock. It may also take some time to receive and fill a prescription.

If a patient uses EC often, I suggest other, more effective types of contraception. There are many different options. These include

  • daily birth control pills

  • vaginal rings

  • skin patches

  • injections given every 3 months

There also are long-acting reversible birth control options, such as implants and IUDs. For women who need EC and also want long-term contraception, the copper IUD is a good choice. It can prevent pregnancy for many years.

With so many choices, there’s no need to think about birth control every day, every month—or even every year—if you don’t want to.

4. Does EC affect future fertility?

None of the EC methods have any effect on future fertility.

5. Do I need to see a doctor after using EC?

Women usually don’t need to see a health care professional after EC use. But you should get medical care if there are signs of pregnancy, such as a period that hasn’t come a week after it’s expected.

Get medical care right away if you have

  • abdominal pain you can’t control with over-the-counter pain relievers, such as ibuprofen

  • heavy vaginal bleeding that requires you to change your sanitary pad or tampon every 1 to 2 hours

Pain and heavy bleeding could be a sign of an ectopic pregnancy, which is a pregnancy located outside of the uterus. These symptoms should be checked out by a health care professional.

Final thoughts

EC is a safe, effective way to prevent pregnancy after unprotected sex. But you should talk with your ob-gyn if you use EC and would like more reliable, cost-effective birth control. There are many different choices. We want to help you find the option that works best for you.

Published: November 2021

Last reviewed: November 2021

Copyright 2023 by the American College of Obstetricians and Gynecologists. All rights reserved. Read copyright and permissions information.

This information is designed as an educational aid for the public. It offers current information and opinions related to women's health. It is not intended as a statement of the standard of care. It does not explain all of the proper treatments or methods of care. It is not a substitute for the advice of a physician. Read ACOG’s complete disclaimer.

About the Author
Cynthia Abraham, MD
Dr. Cynthia Abraham

Dr. Abraham is an obstetrician–gynecologist (ob-gyn) and assistant professor in the Department of Obstetrics, Gynecology, and Reproductive Science at the Icahn School of Medicine at Mount Sinai in New York, New York. She is a fellow of the American College of Obstetricians and Gynecologists.