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Emergency contraception (EC), or emergency postcoital contraception, refers to contraceptive measures that, if taken after sex, may prevent pregnancy.

Forms of EC include:

  • Emergency contraceptive pills (ECPs)—sometimes simply referred to as emergency contraceptives (ECs) or the "morning-after pill"—are drugs that act both to prevent ovulation or fertilization and possibly post-fertilization implantation of a blastocystembryo). ECPs are distinct from medical abortion methods that act after implantation.[1] (
  • Intrauterine devices (IUDs)—usually used as a primary contraception method, but sometimes used as emergency contraception.

As its name implies, EC is intended for occasional use, when primary means of contraception fail. Since EC methods act before implantation, they are medically and legally considered forms of contraception. Some scientists believe that EC may possibly act after fertilization (see Mechanism of action), a possibility that leads some to consider EC an abortifacient.

Emergency contraceptive pills (ECPs)

Emergency contraceptive pills (sometimes referred to as emergency hormonal contraception (EHC) in the U.K.) may contain higher doses of the same hormones (estrogens, progestins, or both) found in regular combined oral contraceptive pills. Taken after unprotected sexual intercourse, such higher doses may prevent pregnancy from occurring.[2] Mifepristone[citation needed] can be used as EC, but is an anti-hormonal drug, and does not contain estrogen or progestins.

The phrase "morning-after pill" is a misnomer; ECPs are effective when used shortly before intercourse, and are licensed for use up to 72 hours after sexual intercourse and the WHO says they can be used for up to 5 days after contraceptive failure (see "Effectiveness" section below).

Types of ECPs

The progestin-only method uses the progestin levonorgestrel in a dose of 1.5 mg, either as two 750 μg doses 12 hours apart, or more recently as a single dose. Progestin-only EC is available as a dedicated emergency contraceptive product under many names worldwide, including: in the U.S., Canada and Honduras as Plan B; in the U.K., Ireland, Australia, New Zealand, Portugal and Italy as Levonelle; in South Africa as Escapelle; in 44 nations including France, most of Western Europe, India, and several countries in Africa, Asia and Latin America as NorLevo; and in 44 nations including most of Eastern Europe, Mexico and many other Latin American countries, Portugal, Australia and New Zealand, Israel, China, Hong Kong, Taiwan and Singapore as Postinor-2.[3]

The combined or Yuzpe regimen uses large doses of both estrogen and progestin, taken as two doses at a 12-hour interval. This method is now believed to be less effective and less well-tolerated than the progestin-only method.[4] It is possible to obtain the same dosage of hormones, and therefore the same effect, by taking several regular combined oral contraceptive pills. For example, 4 Ovral pills are the same as 4 Preven pills.[5][6] The United States Food and Drug Administration (FDA) approved this off-label use of certain brands of regular combined oral contraceptive pills in 1997.[2][5][7]

The drug mifepristone may be used either as an ECP or as an abortifacient, depending on whether it is used before or after implantation. In the USA, it is most commonly used in 200- or 600-mg doses as an abortifacient,[8] but in China it is commonly used as emergency contraception. As EC, a low dose of mifepristone is slightly less effective than higher doses, but has fewer side effects.[9] As of 2000, the smallest dose available in the USA was 200 mg.[10][11] A review of studies in humans concluded that the contraceptive effects of the 10-mg dose are due to its effects on ovulation,[12] but understanding of its mechanism of action remains incomplete. Higher doses of mifepristone can disrupt implantation and, unlike levonorgestrel, mifepristone is effective in terminating established pregnancies. Mifepristone, however, is not approved for emergency contraceptive use in the United States.

Morning-after pills (ECPs) are not to be confused with the “abortion pill”, otherwise known as RU486, mifestone, or Mifeprex. According to the International Federation of Gynecology and Obstetrics, “EC is not an abortifacient because it has its effect prior to the earliest time of implantation.” Since they act before implantation, they are considered medically and legally to be forms of contraception.

Effectiveness of ECPs

The effectiveness of emergency contraception is presented differently from the effectiveness of ongoing methods of birth control: it is expressed as a percentage reduction in pregnancy rate for a single use of EC. Different ECP regimens have different effectiveness levels, and even for a single regimen different studies may find varying rates of effectiveness. Using an example of "75% effective", an article in American Family Physician explains the effectiveness calculation thus:

... these numbers do not translate into a pregnancy rate of 25 percent. Rather, they mean that if 1,000 women have unprotected intercourse in the middle two weeks of their menstrual cycles, approximately 80 will become pregnant. Use of emergency contraceptive pills would reduce this number by 75 percent, to 20 women.[13]

The progestin-only regimen (using levonorgestrel) is reported by the U.S. FDA to have an 89% effectiveness. As of 2006, the labeling on the U.S. brand Plan B explained this effectiveness rate by stating, "Seven out of every eight women who would have gotten pregnant will not become pregnant."[14]

In 1999, a meta-analysis of eight studies of the combined (Yuzpe) regimen concluded that the best point estimate of effectiveness was 74%.[15] A 2003 analysis of two of the largest combined (Yuzpe) regimen studies, using a different calculation method, found effectiveness estimates of 47% and 53%.[16]

For both the progestin-only and Yuzpe regimens, the effectiveness of emergency contraception is highest when taken within 12 hours of intercourse and declines over time.[4][17][18] While most studies of emergency contraception have only enrolled women within 72 hours of unprotected intercourse, a 2002 study by the World Health Organization (WHO) suggested that reasonable effectiveness may continue for up to 120 hours (5 days) after intercourse.[19]

For 10 mg of mifepristone taken up to 120 hours (5 days) after intercourse, the combined estimate from three trials was an effectiveness of 83%.[20] A review found that many trials found a regimen of 25–50 mg of mifepristone to have higher effectiveness. However, when reviewers looked at only high-quality trials, the difference in effectiveness was not statistically significant.[21]

History of calculation methods

Early studies of emergency contraceptives did not attempt to calculate a failure rate; they simply reported the number of women who became pregnant after using an emergency contraceptive. Since 1980, clinical trials of emergency contraception have first calculated probable pregnancies in the study group if no treatment were given. The effectiveness is calculated by dividing observed pregnancies by the estimated number of pregnancies without treatment.[22]

Placebo-controlled trials that could give a precise measure of the pregnancy rate without treatment would be unethical, so the effectiveness percentage is based on estimated pregnancy rates. These are currently estimated using variants of the calendar method.[23] Women with irregular cycles for any reason (including recent hormone use such as oral contraceptives and breastfeeding) must be excluded from such calculations. Even for women included in the calculation, the limitations of calendar methods of fertility determination have long been recognized. In their April 2007 emergency review article, Trussell and Raymond note:

Calculation of effectiveness, and particularly the denominator of the fraction, involves many assumptions that are difficult to validate. Therefore, reported figures on the efficacy of emergency contraception may be underestimates or, more probably, overestimates. Yet, precise estimates of efficacy may not be highly relevant to many women who have had unprotected intercourse, since ECPs are often the only available treatment.[24]

Recently, hormonal assay has been suggested as a more accurate method of estimating fertility for EC studies.[25]


Existing pregnancy is not a contraindication in terms of safety, as there is no known harm to the woman, the course of her pregnancy, or the fetus if progestin-only or combined emergency contraception pills are accidentally used, but EC is not indicated for a woman with a known or suspected pregnancy because it is not effective in women who are already pregnant.

The World Health Organization (WHO) lists no medical condition for which the risks of emergency contraceptive pills outweigh the benefits.[30] The American Academy of Pediatrics[24][26][27] (AAP) and experts on emergency contraception have concluded that progestin-only ECPs may be preferable to combined ECPs containing estrogen in women with a history of blood clots, stroke, or migraine.

The AAP, American College of Obstetricians and Gynecologists (ACOG), U.S. Food and Drug Administration, WHO, Royal College of Obstetricians and Gynaecologists, and other experts on emergency contraception state that there are no medical conditions in which progestin-only ECPs are contraindicated.[24][26][27][28][29][30][31] RCOG specifically note current venous thromboembolism, current or past history of breast cancer, inflammatory bowel disease, and acute intermittent porphyria as conditions where the advantages of using emergency contraceptive pills generally outweigh the theoretical or proven risks.[31]

The herbal preparation of St John's wort and some enzyme-inducing drugs (e.g. anticonvulsantsrifampicin) may reduce the effectiveness of ECP, and a larger dose may be required.[33][34] or

The AAP, ACOG, FDA, WHO, RCOG, and experts on emergency contraception have concluded that ECPs, like all other contraceptives, reduce the absolute risk of ectopic pregnancy by preventing pregnancies, and that the best available evidence, obtained from over 7,800 women in randomized controlled trials, indicates there is no increase in the relative risk of ectopic pregnancy in women who become pregnant after using progestin-only ECPs.[24][26][27][28][29][30][31][32][33][35]

Side effects

The most common side effect reported by users of emergency contraceptive pills was nauseavomiting is much less common and unusual with levonorgestrel-only ECPs (18.8% of 979 Yuzpe regimen users and 5.6% of levonorgestrel-only users in the 1998 WHO trial; 1.4% of 2,720 levonorgestrel-only users in the 2002 WHO trial).[4][19][33] Anti-emetics are not routinely recommended with levonorgestrel-only ECPs.[33][36] If a woman vomits within 2 hours of taking a levonorgestrel-only ECP, she should take a further dose as soon as possible.[33][37] (50.5% of 979 Yuzpe regimen users and 23.1% of 977 levonorgestrel-only users in the 1998 WHO trial; 14.3% of 2,720 levonorgestrel-only users in the 2002 WHO trial);

Other common side effects (each reported by less than 20% of levonorgestrel-only users in both the 1998 and 2002 WHO trials) were abdominal pain, fatigue, headache, dizziness, and breast tenderness.[4][19][33] Side effects usually do not occur for more than a few days after treatment, and they generally resolve within 24 hours.[24]

Temporary disruption of the menstrual cycle is also commonly experienced. If taken before ovulation, the high doses of progestogen in levonorgestrel treatments may induce progestogen withdrawal bleeding a few days after the pills are taken. One study found that about half of women who used levonorgestrel ECPs experienced bleeding within 7 days of taking the pills.[38]luteal phase, thus delaying menstruation by a few days.[39] Mifepristone, if taken before ovulation, may delay ovulation by 3–4 days.[40] (Delayed ovulation may result in a delayed menstruation.) These disruptions only occur in the cycle in which ECPs were taken; subsequent cycle length is not significantly affected.[38] If a woman's menstrual period is delayed by a week or more, it is advised that she take a pregnancy test.[41] (Earlier testing may not give accurate results.) If levonorgestrel is taken after ovulation, it may increase the length of the

Intrauterine device (IUD) for emergency contraception

An alternative to emergency contraceptive pills is the copper-T intrauterine device (IUD) which can be used up to 5 days after unprotected intercourse to prevent pregnancy. Insertion of an IUD is more effective than use of Emergency Contraceptive Pills - pregnancy rates when used as emergency contraception are the same as with normal IUD use. IUDs may be left in place following the subsequent menstruation to provide ongoing contraception (3–10 years depending upon type).[42]

Postcoital high-dose progestin-only oral contraceptive pills as ongoing contraception

One brand of levonorgestrel pills, Postinor, is marketed as an ongoing method of postcoital contraception.[43] However, there are serious drawbacks to such use of postcoital high-dose progestin-only oral contraceptive pills, especially if they are not used according to their package directions, but are instead used according to the package directions of emergency contraceptive pills:

  • Due to the increasing severity of side effects with frequent use, Postinor is only recommended for women who have intercourse four or fewer times per month.[43][44]
  • If not used according to their package directions, but instead used according to the directions of levonorgestrel emergency contraceptive pills (up to 72 hours after intercourse), they would be estimated to have a "perfect-use" (when not used according to their package directions but used as directed on the package directions for levonorgestrel emergency contraception pills) pregnancy rate of 20% per year when used as the sole means of contraception (as compared to a 40% annual pregnancy rate for the Yuzpe regimen).[45] These failure rates would be higher than those of almost all other birth control methods, including the rhythm method and withdrawal.[46]
  • Like all hormonal methods, postcoital high-dose progestin-only oral contraceptive pills do not protect against sexually transmitted infections.[47]

ECPs are generally recommended for backup or "emergency" use, rather than as the primary means of contraception. They are intended for use when other means of contraception have failed—for example, if a woman has forgotten to take a birth control pill or when a condom is torn during sex ( although condoms tend to break in which case i recommend birth control pill as the better option).

Emergency contraception
B.C. type Hormonal (progestin or others) or intra-uterine
First use 1970s
Failure rates (per use)
Perfect use ECP: see article text
IUD: under 1%
Typical use ?%
User reminders Pregnancy test required if no period seen after 3 weeks
Clinic review Recommended to consider need screen STDs or consider ongoing routine contraceptive options
Advantages and disadvantages
STD protection No
Periods ECP may disrupt next menstrual period by couple days. IUDs may make menstruation heavier and more painful
Benefits IUDs may be subsequently left in place for ongoing contraception
Risks As per methods
Medical notes
Combined estrogrogen/progestin pills of Yuzpe regimen now superseded by better tolerated and more effective progestin-only pill.
ECP licensed for use within 3 days of unprotected intercourse and IUDs within 5 days.


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