Medical Health Encyclopedia

Emergency contraception

Not every woman who has unprotected intercourse will get pregnant. The risk of pregnancy depends on many factors, especially the time in the menstrual cycle that intercourse occurs. For instance, if 100 women have unprotected intercourse once in the middle 2 weeks of their menstrual cycles, about 8 will become pregnant. If they all use emergency contraception within 72 hours of intercourse, only 1 to 2 will become pregnant.

RISKS:

Mild and often unpleasant side effects from emergency contraception medications are common, such as nausea, vomiting, abdominal pain, fatigue, headache, and changes in menstrual bleeding. Nausea and vomiting are the most troublesome side effects -- nausea occurs about 50% of the time and vomiting about 20% of the time after emergency contraceptive pills are taken.

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Some doctors recommend taking an anti-emetic medication (a drug to prevent nausea and vomiting) before taking the emergency contraception pills to prevent these side effects. Progesterone-only emergency contraceptives cause less nausea and vomiting than methods that contain both progesterone and estrogen-like medications.

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. Still, 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.

Emergency contraception drugs do not appear to harm an early pregnancy. However, women who believe that they are already pregnant and may have been for longer than several days should not take such drugs, 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.