Emergency contraception most likely works by preventing or delaying the release of an egg from a woman's ovaries. This method prevents pregnancy in the same way as regular birth control pills.
TYPES OF EMERGENCY CONTRACEPTION
Two emergency contraceptive pills may be bought without a prescription:
- 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.
- Either may be taken for up to 5 days after unprotected intercourse.
Ulipristal acetate (ella) is a new type of emergency contraception pill that requires a prescription from a health care provider.
- Ulipristal is taken as a single tablet.
- It may be taken up to 5 days after unprotected sex.
Two other methods that may be used to prevent pregnancy after unprotected sex are:
- Birth control pills. Talk to your health care provider about the correct dosage. In general, you must take 2 - 5 birth control pills at the same time to have the same protection.
- A copper-releasing intrauterine device (IUD) may be used as an alternative emergency contraception method. It must be inserted by your health care provider within 5 days of having unprotected sex. Your doctor can remove it after your next period, or you may choose to leave it in place to provide ongoing birth control.
MORE ABOUT EMERGENCY CONTRACEPTIVE PILLS
Women ages 17 and older can buy Plan B One-Step and Next Choice at a pharmacy without a prescription or visit to the doctor. Younger girls need to contact a health care provider to get a prescription for these pills.
Emergency contraception works best when you use it within 24 hours of having sex. However, it may still prevent pregnancy for up to 5 days after you first had sex.
Emergency contraception may cause side effects. Most are mild. They may include:
- Changes in menstrual bleeding
- Nausea and vomiting
After you use emergency contraception, your next menstrual cycle may start earlier or later than usual. Your menstrual flow may be lighter or heavier than usual.
- Most women get their next period within 7 days of the expected date.
- If you do not get your period within 3 weeks after taking emergency contraception, you might be pregnant. Contact your health care provider.
Sometime, emergency contraception does not work. However, research suggests that emergency contraceptives have no long-term effects on the pregnancy or developing baby.
OTHER IMPORTANT FACTS
You should not use emergency contraception if:
- You think you have been pregnant for several days
- You have vaginal bleeding for an unknown reason (talk to your health care provider first)
You may be able to use emergency contraception even if you cannot regularly take birth control pills. Talk to your health care provider about your options.
Emergency contraception should not be used as a routine birth control method. It is less effective at preventing pregnancies than most types of birth control.
Tibbles CD. Selected gynecologic disorders. In: Marx JA, Hockberger RS, Walls RM, et al, eds. Rosen’s Emergency Medicine: Concepts and Clinical Practice. 7th ed. Philadelphia, Pa: Mosby Elsevier; 2009:chap 98.
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.
Armstrong C. ACOG recommendations on emergency contaception. Am Fam Physician. November 15, 20120;82(10;1278.