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Emergency Contraception

By Laura Sech, MD, Family Planning Fellow, Department of Obstetrics and Gynecology, University of Southern California Keck School of Medicine ; Daniel R. Mishell, Jr., MD, The Lyle G. McNeile Professor, Department of Obstetrics and Gynecology;Chief Physician, Keck School of Medicine, University of Southern California;Women's and Children's Hospital, Los Angeles County and University of Southern California Medical Center ; Emily Silverstein, MD, Research Project Manager, Department of Obstetrics and Gynecology, University of Southern California Keck School of Medicine

Emergency contraception is used after an act of unprotected sexual intercourse or after an occasion when a contraceptive method fails (for example, when a condom breaks).

Emergency contraception decreases the chance of pregnancy after one act of unprotected intercourse, including when the act occurs near the time the egg is released (ovulation)—when conception is most likely. Overall, the chance of pregnancy is about 5% after one act of unprotected sex, but closer to ovulation, it is about 20%. The sooner emergency contraception is used, the more likely it is to be effective.

Available options include

  • Levonorgestrel: This hormone is most commonly used. It is a progestin often taken in lower doses for contraception. Levonorgestrel is taken by mouth. Women may take a dose, followed by another dose 12 hours later. Or they may take one higher dose. The chance of pregnancy is about 2 to 3%. However, the chance is higher (2 to 9%) in women who are obese. The dose is more effective the sooner it is taken, but to be effective, it must be taken within 3 days (72 hours) after unprotected intercourse. These tablets are available over-the-counter without restriction for women of all ages who have had unprotected intercourse.

  • Ulipristal acetate: One dose of this drug is taken. It is more effective than levonorgestrel. It must be taken within 5 days (120 hours) after unprotected intercourse. The chance of pregnancy is about 1.5%. A prescription is needed. However, this form of emergency contraception may be purchased through an online pharmacy (at and delivered via mail to the person's home.

  • Combination oral contraceptives: A combination oral contraceptive (estrogen plus levonorgestrel) can be used, but it is slightly less effective than levonorgestrel or ulipristal acetate. Two combination tablets are taken, followed by two more tablets 12 hours later. A high dose of estrogen is used. It often causes nausea and sometimes causes vomiting. Doctors may recommend drugs that can help prevent nausea and vomiting.

  • Insertion of a copper intrauterine device (IUD—see Intrauterine Devices): To be effective, the IUD must be inserted within 5 days of unprotected sex. The chance of pregnancy after insertion of the IUD is 0.2%—the same as it is when the IUD is used for regular birth control. Also, after its insertion, the IUD can be left in place to provide continued contraception for up to 10 years.

The drugs used for emergency contraception (the so-called morning-after pills) inhibit ovulation. They are more commonly used as emergency contraception than are IUDs, even though a copper IUD is the most effective form of emergency contraception.

Drugs Mentioned In This Article

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* This is the Consumer Version. *