Commonly used emergency contraception (EC) regimens include
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:
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.
Last full review/revision June 2013 by Laura Sech; Penina Segall-Gutierrez, MD, MSc; Emily Silverstein; Daniel R. Mishell, Jr., MD
Content last modified August 2013