Emergency Contraception

Commonly used emergency contraception 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. A urine pregnancy test 2 weeks after use of emergency contraception is recommended.

When a copper-bearing or 52-mg levonorgestrel-releasing IUD is used for emergency contraception, it must be inserted within 5 days of unprotected intercourse (or within 5 days of suspected ovulation, if the timing of ovulation can be estimated). The pregnancy rate with is 0.1% for emergency contraception with the copper-releasing IUD and 0.3% for the 52-mg levonorgestrel-releasing IUD (1 General reference Commonly used emergency contraception regimens include Insertion of a copper-bearing T380A IUD within 5 days of unprotected intercourse Insertion of a 52-mg levonorgestrel-releasing IUD, which... read more ). Also, the IUD can be left in place to be used for long-term contraception. As emergency contraception, the copper-bearing IUD may affect blastocyst implantation; however, it does not appear to disrupt an already established pregnancy. The resumption of menses plus a negative pregnancy test reliably excludes pregnancy; a pregnancy test should be done 2 to 3 weeks after insertion to be sure that an unintended pregnancy has not occurred before insertion.

Oral levonorgestrel (1.5 mg, single dose) used as emergency contraception prevents pregnancy by inhibiting or delaying ovulation. The probability of pregnancy is reduced by 85% after oral levonorgestrel emergency contraception, which has a pregnancy rate of 2 to 3%. However, overall risk reduction depends on the following:

In the US, oral levonorgestrel emergency contraception is available behind pharmacy counters without a prescription. A hormonal contraceptive may be started at the same time as use of oral levonorgestrel as part of a quick-start protocol. A backup method (such as a condom) is recommended for 7 days.

Ulipristal acetate (a single oral dose of 30 mg), a progestin-receptor modulator, as emergency contraception has a pregnancy rate of about 1.5% and is thus more effective than oral 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 kg/m2, 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 emergency contraception. Ulipristal acetate is available by prescription only. Hormonal birth control should not be started until 6 days after use of ulipristal acetate, since progestins may interfere with emergency contraceptive efficacy. If hormonal contraception is started on day 6, a backup method (such as a condom) should be used for 7 days.

There are no absolute contraindications to levonorgestrel or ulipristal acetate emergency contraception. Oral levonorgestrel and ulipristal emergency contraception should be taken as soon as possible and within 120 hours of unprotected intercourse.

The Yuzpe method is another regimen. It consists of 2 tablets, each containing ethinyl estradiol 50 mcg and levonorgestrel 0.25 mg, followed by 2 more tablets taken 12 hours later but within 72 hours of unprotected intercourse. The high estrogen dose often causes nausea and may cause vomiting. A hormonal contraceptive may be started at the same time as use of the Yuzpe method, as part of a quick-start protocol. A backup method (such as a condom) is recommended for 7 days. The Yuzpe method is less effective than other methods; thus, it is no longer recommended except when women do not have access to other methods.