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Emergency contraception

Contents of this page:


Intrauterine device
Intrauterine device
Side sectional view of female reproductive system
Side sectional view of female reproductive system
Hormone-based contraceptives
Hormone-based contraceptives
Birth control methods
Birth control methods

Alternative Names    Return to top

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

Definition    Return to top

Emergency contraception is a method of birth control that can be used within 3 days of sexual intercourse.

Information    Return to top

Emergency contraception is a method to prevent pregnancy in women who have had unprotected sex. It can be used following many different situations including rape, unplanned acts of intercourse, or when a birth control method fails. For example, if a condom breaks, a diaphragm slips out of place, or 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.

Unlike most types of birth control, which must be put in place or taken before intercourse, emergency contraception can be used up to 5 days after intercourse.


Several types of emergency contraception drugs are available.

Birth control pills can be used for emergency contraception. You must take two to five "regular" pills together to equal one dose of emergency contraception.

There is only one FDA-approved emergency contraception pill. The brand name is Plan B. It is similar to some birth control pills, but contains higher levels of hormones. Plan B contains two pills, each containing levonorgestrel, which you take at the same time. It is available over-the-counter for purchase by anyone age 18 and older and by prescription for younger patients.

Emergency contraception pills work best when taken as soon as possible after intercourse. Ideally, the medicine should be taken within 72 hours after unprotected intercourse, but it may be effective for up to 5 days.

Emergency contraceptives work by preventing or delaying the release of an egg (ovulation).

An intrauterine device (IUD) may help prevent against contraception if put into place within 7 days after unprotected intercourse. An IUD is a birth control device that is inserted into a woman's uterus by a health care provider. However, IUDs are intended to provide long-term birth control for 1-10 years.

Emergency contraception pills prevent about 75 - 89% of pregnancies that occur after unprotected sexual intercourse. Emergency contraception by IUD insertion is even more effective. However, pregnancy still occur in a small number of cases in those who use emergency contraception.


Mild and often unpleasant side effects from emergency contraception medication may include nausea, vomiting, 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.

Some doctors recommend taking a drug to prevent nausea and vomiting (an antiemetic medication) before taking the emergency contraception pills to prevent such side effects.

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.

IUD placement has risks of pelvic infection and uterine injury, although these are quite rare. Long-term use of an IUD for birth control may cause side effects, such as heavy menstrual bleeding and painful menstrual cramps.


Women who believe that they are already pregnant and may have been for longer than several days should not take emergency contraception medicine, since their effects have not been well studied. 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.

References    Return to top

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.

Update Date: 2/19/2009

Updated by: Linda Vorvick, MD, Family Physician, Seattle Site Coordinator, Lecturer, Pathophysiology, MEDEX Northwest Division of Physician Assistant Studies, University of Washington School of Medicine; and 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.

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