Printer Friendly Version Email A Friend Add This Increase Text Size Decrease Text Size

Emergency contraception



Emergency contraception is a method to prevent pregnancy in women who have had unprotected sex, or for whom a barrier method has failed (slipped condom, diaphragm, or cervical cap, or broken condom).

Alternative Names

Morning-after pill; Postcoital contraception; Birth control - emergency; Plan B


Emergency contraception may be used following many different situations, including:

  • After intercourse in which no birth control method is used
  • Sexual assault or rape
  • When a condom breaks or a diaphragm slips out of place
  • When a woman forgets to take birth control pills

Emergency contraception medicine is not the same as the "abortion pill." A woman who knows she is pregnant takes the abortion pill with the intent to end an early pregnancy (usually 4 to 7 weeks after conception). Emergency contraception pills are taken after unprotected sex to prevent pregnancy from occurring.


Several types of emergency contraception drugs are available.

Two emergency contraceptive pills have been approved:

  • Plan B One-Step is a single tablet that contains 1.5 mg of levonorgestrel.
  • Next Choice is taken as two doses, which each contain 0.75 mg of levonorgestrel. Both pills can be taken at the same time or as two separate doses 12 hours apart.

Birth control pills, if available, can be used for emergency contraception. You must take two to five "regular" pills together to equal one dose of emergency contraception. It is best to talk to your health care provider about the correct dosage before doing this.

An alternative emergency contraception relies on insertion of a copper-releasing intrauterine device (IUD) within 5 days (120 hours) after unprotected intercourse. It can be removed after your next period, or left in place to provide ongoing contraception. The copper IUD reduces the risk of pregnancy by 99.9%.


Both types Plan B One-Step and Next Choice are available over-the-counter (without a prescription) to women 17 years and older. Women younger than 17 can contact their health care provider to get a prescription for these pills. These pills are still considered safe to use for this younger age group.

Emergency contraceptives work best when taken within the first 24 hours after intercourse.

  • About 7 out of 8 women who would have gotten pregnant do not become pregnant if emergency contraceptives are taken within 72 hours.
  • These pills may still prevent pregnancy for up to 5 days after unprotected intercourse.

Emergency contraceptives work mostly by preventing or delaying the release of an egg (ovulation) - the same way that taking regular birth control pills works. It is possible that these drugs work by preventing an egg from being fertilized by a sperm, or by preventing a fertilized egg from implanting in (sticking to) the walls of your uterus (womb).

Mild and often unpleasant side effects from emergency contraception medication may include:

  • Abdominal pain, fatigue, headache, and changes in menstrual bleeding.
  • Nausea and vomiting are most common when an estrogen-containing pill is used. These side effects are less common with Plan B, which contains a synthetic progesterone.

After taking emergency contraception, a woman's next menstrual cycle may start earlier or later than expected and the menstrual flow may be lighter or heavier than usual.

  • Most women will start their next period within 7 days of the expected date.
  • If a woman's menstrual bleeding does not start within 3 weeks after taking emergency contraception, she might be pregnant and should call or visit her health care provider.


Women who believe that they are already pregnant and may have been for longer than several days should not take emergency contraception medicine. Also, women who have vaginal bleeding for an unknown reason should discuss this with their health care provider before taking emergency contraception.

Women who cannot take birth control pills regularly may often still be able to use emergency contraceptives, but they should also discuss this option with their health care provider.

If emergency contraception fails and the woman becomes pregnant, there do not appear to be any long-term effects on the pregnancy or the fetus.

Emergency contraception should not be used as a routine birth control method, because it is actually less effective at preventing pregnancies than most types of birth control.


Amy JJ, Tripathi V. Contraception for women: an evidence based overview. BMJ. 2009;339:b2895.doi:10.1136/bmj.b2895.

Prine L. Emergency contraception: myths and facts. Obstet Gynecol Clin N Am. 2007;34:127–136

Mischell DR. Family planning: contraception, sterilization, and pregnancy termination. In: Katz VL, Lentz GM, Lobo RA, Gershenson DM, eds. Comprehensive Gynecology. 5th ed. Philadelphia, Pa: Mosby Elsevier; 2007:chap 14.

Related Taxonomy

Review Date: 3/30/2010
Reviewed By: Susan Storck, MD, FACOG, Chief, Eastside Department of Obstetrics and Gynecology, Group Health Cooperative of Puget Sound, Redmond, Washington; Clinical Teaching Faculty, Department of Obstetrics and Gynecology, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.
A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission ( URAC's accreditation program is an independent audit to verify that A.D.A.M. follows rigorous standards of quality and accountability. A.D.A.M. is among the first to achieve this important distinction for online health information and services. Learn more about A.D.A.M.'s editorial policy, editorial process and privacy policy. A.D.A.M. is also a founding member of Hi-Ethics and subscribes to the principles of the Health on the Net Foundation (
The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. © 1997- 2009 A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.

Home Page
Why Choose Us
Website Terms of Use

Visitor & Patient Info
Patient Portal
We Speak Your Language
Patient Privacy
Contact Us

Find a Physician
Medical Services
Maimonides In the News
Directions & Parking

Medical Education
Career Opportunities
Nurses & Physicians
Staff Intranet Access
Maimonides Medical Center    |    4802 Tenth Avenue    |    Brooklyn, NY 11219    |    718.283.6000    |