Commonly used emergency contraception (EC) regimens include
Insertion of a copper-bearing T380A IUD within 5 days of unprotected intercourse
Levonorgestrel 0.75 mg orally in 2 doses 12 hours apart within 120 hours of unprotected intercourse (although efficacy is lower after 72 hours)
Levonorgestrel 1.5 mg orally once within 120 hours of unprotected intercourse
Ulipristal acetate 30 mg orally once within 120 hours 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.
Emergency contraception 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 body mass index (BMI; levonorgestrel EC is less effective than ulipristal acetate in obese women with a BMI > 30)
Levonorgestrel EC is available behind pharmacy counters without a prescription.
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. Ulipristal acetate is available by prescription only.
There are no absolute contraindications to levonorgestrel or ulipristal acetate EC. Levonorgestrel and ulipristal EC 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. 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.
EC can be given when another hormonal contraceptive is started as part of a quick-start protocol. A urine pregnancy test 2 weeks after use of EC is recommended.
Usually, hormones (eg, ulipristal acetate, levonorgestrel) are used for emergency contraception (EC); they are taken as soon as possible after 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.