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Emergency Contraception (EC)

by Laura Sech, Penina Segall-Gutierrez, MD, MSc; Emily Silverstein; Daniel R. Mishell, Jr., MD

Commonly used emergency contraception (EC) regimens include

  • Insertion of a copper-bearing T380A IUD within 5 days of unprotected intercourse

  • Levonorgestrel 0.75 mg po in 2 doses 12 h apart within 120 h of unprotected intercourse

  • Levonorgestrel 1.5 mg po once within 120 h of unprotected intercourse

  • Ulipristal acetate 30 mg po once within 120 h of unprotected intercourse

For women who have regular menses, the risk of pregnancy after a single act of intercourse is about 5%. This risk is 20 to 30% if intercourse occurs at midcycle.

When a copper-bearing IUD is used for EC, it must be inserted within 5 days of unprotected intercourse or within 7 days of suspected ovulation. The pregnancy rate with this EC method is 0.1%. Also, the IUD can be left in place to be used for long-term contraception. As EC, the copper-bearing IUD may affect blastocyst implantation; however, it does not appear to disrupt an already established pregnancy.

EC with levonorgestrel prevents pregnancy by inhibiting or delaying ovulation. The probability of pregnancy is reduced by 85% after levonorgestrel EC, which has a pregnancy rate of 2 to 3%. However, overall risk reduction depends on the following:

  • The woman's risk of pregnancy without EC

  • The time in the menstrual cycle that EC is given

  • The woman's BMI (levonorgestrel EC is less effective than ulipristal acetate in obese women with a body mass index [BMI] > 30)

Ulipristal acetate (a progestin-receptor modulator) has a pregnancy rate of about 1.5% and is thus more effective than levonorgestrel. Ulipristal acetate, like levonorgestrel, prevents pregnancy primarily by delaying or inhibiting ovulation. Although ulipristal acetate is more effective than levonorgestrel for women with a BMI > 30, its effectiveness also decreases as BMI increases. Thus, in obese women who strongly desire to avoid an unintended pregnancy, the copper-bearing IUD is the preferred method for EC.

There are no absolute contraindications to levonorgestrel or ulipristal acetate EC. Levonorgestrel EC is available behind pharmacy counters without a prescription. Ulipristal acetate is available by prescription only. Levonorgestrel and ulipristal EC should be taken as soon as possible and within 120 h of unprotected intercourse.

Another regimen (the Yuzpe method) consists of 2 tablets, each containing ethinyl estradiol 50 mcg and levonorgestrel 0.25 mg, followed by 2 more tablets taken 12 h later but within 72 h of unprotected intercourse. The high estrogen dose often causes nausea and may cause vomiting. This method is also less effective than other methods; thus, it is no longer recommended except when women do not have access to other methods.

EC can be given when another hormonal contraceptive is started as part of a quick-start protocol. A urine pregnancy test 2 wk after use of EC is recommended.

Key Points

  • Usually, hormones (eg, ulipristal acetate, levonorgestrel) are used for emergency contraception (EC); they are taken as soon as possible within 120 h of unprotected intercourse.

  • A copper-bearing IUD, inserted within 5 days of unprotected intercourse, is also effective and can be left in place for long-term contraception.

  • Pregnancy rates are 1.5% with ulipristal acetate, 2 to 3% with levonorgestrel, and 0.1% with a copper-bearing IUD.

  • Likelihood of pregnancy after hormonal EC depends on pregnancy risk without EC, time in the menstrual cycle that EC is taken, and the woman's BMI.

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