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{{Emergency contraception}}

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==Overview==
Emergency contraceptive pills (ECPs)&mdash;sometimes simply referred to as emergency contraceptives (ECs) or the morning-after pill &mdash;are drugs that act both to prevent [[ovulation]] or [[fertilization]] and possibly post-fertilization [[Pregnancy|implantation]] of a [[blastocyst]] ([[embryo]]). Emergency contraceptive pills (sometimes referred to as emergency hormonal contraception (EHC) in the U.K.) may contain higher [[dose]]s of the same [[hormone]]s ([[estrogen]]s, [[progestin]]s, or both) found in regular [[combined oral contraceptive pill]]s. Taken after [[unprotected sex|unprotected sexual intercourse]], such higher doses may prevent pregnancy from occurring. [[Mifepristone]] is another kind of ECP, but is considered an anti-hormonal drug, and does not contain estrogen or progestins. The phrase "morning-after pill" is figurative; ECPs are licensed for use up to 72 hours after sexual intercourse. ECPs are distinct from [[medical abortion]]methods that act after implantation.<ref>A minority view in the medical community, along with many [[pro-life]] advocates, argue for a [[Beginning of pregnancy controversy|different definition of pregnancy]]; see [[Emergency contraception#Controversy in relation to abortion|Controversy section]] for more detail.</ref>

==Emergency Contraceptive Pills==
{{seealso|Emergency contraceptive availability by country}}

===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 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''.<ref name="ecp worldwide">{{cite web |author=Trussell, James; Wynn, Lisa |date=2007-06-28 |title=Emergency Contraceptive Pills Worldwide |url=http://ec.princeton.edu/questions/dedicated.html |publisher=[[Princeton University]] |accessdate=2007-06-30}}</ref>
 
*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.<!--
 --><ref name="who 1998">{{cite journal |author=[[World Health Organization|WHO]] Task Force on Postovulatory Methods of Fertility Regulation |year=1998 |title=Randomised controlled trial of levonorgestrel versus the Yuzpe regimen of combined oral contraceptives for emergency contraception |journal=[[The Lancet|Lancet]] |volume=352 |issue=9126 |pages=428-33 |id=PMID 9708750}}</ref> It is possible to obtain the same dosage of hormones, and therefore the same effect, by taking several regular combined [[oral contraceptive formulations|oral contraceptive pills]]. For example, 4 [[Ovral]] pills are the same as 4 Preven pills.<ref name="ecp US brands">{{cite web |author=OPR & ARHP |date=2007-06-18 |title=Emergency contraception: Pill brands, doses, and instructions |url=http://ec.princeton.edu/questions/dose.html |publisher=[[Princeton University]] |accessdate=2007-06-30}}</ref> The FDA approved this off-label use of certain brands of regular combined oral contraceptive pills in 1997.

*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, 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. As of 2000, the smallest dose available in the USA was 200 mg. Mifepristone, however, is not approved for emergency contraceptive use in the United States. A review of studies in humans concluded that the contraceptive effects of the 10-mg dose are due to its effects on ovulation,<ref>{{cite journal | last = Gemzell-Danielsson | first = K. | coauthors = Marions, L. | title = Mechanisms of action of mifepristone and levonorgestrel when used for emergency contraception | journal =  Human Reproduction Update | volume = 10 | issue = 4 | pages = 341-348 | date = [[2004-06-10]] | publisher = Oxford University Press | url = http://humupd.oxfordjournals.org/cgi/content/abstract/10/4/341|format = [[HTML]] | accessdate = 2006-07-23}}</ref> 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.

*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===
*Progestin-only (levonorgestrel) regimen:
:The original (1999) FDA-approved U.S. product labeling for Plan B said: <blockquote>Plan B reduces the risk of pregnancy following a single act of unprotected sex from about 8% down to 1%. This represents an 89% reduction in risk of pregnancy for this single act of unprotected sex.

:The current (2006) FDA-approved U.S. product labeling for Plan B says: <blockquote>Plan B works best the sooner you use it. If it is taken within 72 hours (3 days) after sex, it will significantly decrease the chance that you will get pregnant. Seven out of every 8 women who would have gotten pregnant will not become pregnant. Plan B works even better than this if taken within the first 24 hours after sex.

*Combined (Yuzpe) regimen:
:The original (1998) FDA-approved U.S. product labeling for Preven (the Yuzpe regimen), referring to Yuzpe regimen ECPs, said: <blockquote>If one hundred women used ECPs correctly in one month, about two women would become pregnant after a single act of intercourse. If no contraception is used about eight women would become pregnant after a single act of intercourse. Therefore, the use of ECPs results in a 75% reduction in the number of pregnancies to be expected if no ECPs were used after unprotected intercourse. Notably some clinical trials have shown that efficacy was greatest when ECPs were taken within 24 hours of unprotected intercourse, decreasing somewhat during each subsequent 24-hour period.

: The effectiveness of emergency contraception is expressed as a percentage reduction in pregnancy rate for a single use of EC. A review article in ''[[American Family Physician]]'' explains the 75% effectiveness rate of the Yuzpe regimen thus: <blockquote>... 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.

*Mifepristone regimen:

In three randomized trials providing individual data of mifepristone 10 mg taken up to 120 hours (5 days) after intercourse, the combined estimate of pregnancies prevented was 83%.<!--
 --><ref name="piaggio 2003">{{cite journal|author=Piaggio G, Heng Z, von Hertzen H, Bilian X, Linan C |year=2003 |title=Combined estimates of effectiveness of mifepristone 10 mg in emergency contraception |journal=Contraception |volume=68 |issue=6 |pages=439-46 |id=PMID 14698074}}</ref> In high quality trials, mifepristone 10 mg had similar effectiveness to mifepristone 25-50 mg, which had similar effectiveness to levonorgestrel 1.5 mg.<!--
 --><ref name="cheng 2004">{{cite journal|author=Cheng L, Gulmezoglu AM, Oel CJ, Piaggio G, Ezcurra E, Look PF |year=2004 |title=Interventions for emergency contraception |journal=Cochrane Database Syst Rev |volume= |issue=3 |pages=CD001324 |id=PMID 15266446 |url=http://www.cochrane.org/reviews/en/ab001324.html}}</ref><!--
 --><ref name="who 2002">{{cite journal |author=von Hertzen H, Piaggio G, Ding J, Chen J, Song S, Bartfai G, Ng E, Gemzell-Danielsson K, Oyunbileg A, Wu S, Cheng W, Ludicke F, Pretnar-Darovec A, Kirkman R, Mittal S, Khomassuridze A, Apter D, Peregoudov A; WHO Research Group on Post-ovulatory Methods of Fertility Regulation |year=2002 |title=Low dose mifepristone and two regimens of levonorgestrel for emergency contraception: a WHO multicentre randomised trial |journa=[[The Lancet|Lancet]] |volume=360 |issue=9348 |pages=1803-10 |id=PMID 12480356}}</ref>

The effectiveness of emergency contraception is highest when taken within 12 hours of intercourse and declines over time.<!--
 --><ref>{{cite journal |author= |year=1999 |title=Counsel women to take ECPs as soon as possible |journal=Contracept Technol Update |volume=20 |issue=7 |pages=75-7 |id=PMID 12295381}}</ref><!--
 --><ref name="who 1999">{{cite journal |author=[[World Health Organization|WHO]]/HRP |year=1999 |title=Levonorgestrel is more effective, has fewer side-effects, than Yuzpe regimen |journal=Prog Hum Reprod Res |volume= |issue=51 |pages=3-5 |id=PMID 12349416 |url=http://www.who.int/reproductive-health/hrp/progress/51/news51_1.en.html#2}}</ref> 
The limit of 72 hours is based on a study by the [[World Health Organization]] (WHO).<!--
 --><ref name="who 1998"/>
A subsequent WHO study has suggested that reasonable effectiveness continues for up to 120 hours (5 days) after intercourse.<!--
 --><ref name="who 2002"/> 
However, many doctors (particularly in the U.K.) advise use of an IUD rather than ECPs for emergency contraception between 72 and 120 hours.{{Fact|date=July 2007}}

====Effectiveness Estimate Calculation====
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 estimated effectiveness using: observed pregnancies divided by the estimated (by cycle day) number of women who would have become pregnant without treatment.<!--
 --><ref>{{cite journal|author=Dixon GW, Schlesselman JJ, Ory HW, Blye RP |title=Ethinyl estradiol and conjugated estrogens as postcoital contraceptives |journal=JAMA |year=1980 |volume=244 |issue=12 |pages=1336-9 |id=PMID 6251288}}</ref> 

In their April 2007 emergency review article, Trussell and Raymond note:
<blockquote>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. A more important consideration for most ECP clients may be the fact that data from both clinical trials and mechanism of action studies clearly show that at least the levonorgestrel regimen of ECPs is more effective than nothing.<ref name="trussell 2007"/></blockquote>
* Eight studies of the progestin-only (levonorgestrel) regimen, that included more than 9,500 women, reported effectiveness estimates between 59% and 94%.<!--
 --><ref name="trussell 2007">{{cite web |author=Trussell J, Raymond EG |month=April |year=2007 |title=Emergency contraception: a cost-effective approach to preventing unintended pregnancy |publisher=[[Princeton University]] |url=http://ec.princeton.edu/questions/ec-review.pdf |accessdate=2007-07-03}}</ref>
* A meta-analysis of eight studies of the combined (Yuzpe) regimen, that included more than 3,800 women and reported effectiveness estimates between 56% and 89%, concluded that the best point estimate of effectiveness was 74%.<!--
 --><ref name="trussell 2007"/><!--
 --><ref name="trussell 1999">{{cite journal |author=Trussell J, Rodriguez G, Ellertson C |year=1999 |title=Updated estimates of the effectiveness of the Yuzpe regimen of emergency contraception |journal=Contraception |volume=59 |issue=3 |pages=147-51 |id=PMID 10382076}}</ref>
* A more recent analysis of two of the largest combined (Yuzpe) regimen studies, using possibly more accurate estimates of conception probabilities by cycle day, found effectiveness estimates of 47% and 53%.<!--
 --><ref name="who 1998"/><!--
 --><ref name="trussell 2007"/><!--
 --><ref name="trussell 2003a">{{cite journal |author=Trussell J, Ellertson C, von Hertzen H, Bigrigg A, Webb A, Evans M, Ferden S, Leadbetter C |year=2003 |title=Estimating the effectiveness of emergency contraceptive pills |journal=Contraception |volume=67 |issue=4 |pages=259-65 |id=PMID 12684144}}</ref><!--
  --><ref name="ellerston 2003">{{cite journal |author=Ellertson C, Webb A, Blanchard K, Bigrigg A, Haskell S, Shochet T, Trussell J |year=2003 |title=Modifying the Yuzpe regimen of emergency contraception: a multicenter randomized controlled trial |journal=Obstet Gynecol |volume=101 |issue=6 |pages=1160-7 |id=PMID 12798518}}</ref>
* Combined data from two randomized trials that directly compared the two regimens, found the levonorgestrel regimen was twice as effective as the Yuzpe regimen.<!--
 --><ref name="who 1998"/><!--
 --><ref name="cheng 2004"/><!--
 --><ref name="trussell 2007"/><!--
 --><ref name="ho 1993">{{cite journal |author=Ho PC, Kwan MS |year=1993 |title=A prospective randomized comparison of levonorgestrel with the Yuzpe regimen in post-coital contraception |journal=Hum Reprod |volume=8 |issue=3 |pages=389-92 |id=PMID 8473453}}</ref><!--
 --><ref name="raymond 2004">{{cite journal |author=Raymond E, Taylor D, Trussell J, Steiner MJ |year=2004 |title=Minimum effectiveness of the levonorgestrel regimen of emergency contraception |journal=Contraception |volume=69 |issue=1 |pages=79-81 |id=PMID 14720626}}</ref>

Placebo-controlled trials that could give a precise measure of effectiveness for EC would be unethical, so the effectiveness percentage is estimated. This is currently done using variants of the calendar method.<!--
 --><ref name="trussell 1996">{{cite journal |author=Trussell J, Ellertson C, Stewart F |year=1996 |title=The effectiveness of the Yuzpe regimen of emergency contraception |journal=Fam Plann Perspect |volume=28 |issue=2 |pages=58-64, 87 |id=PMID 8777940 |url=http://findarticles.com/p/articles/mi_qa3634/is_199603/ai_n8736107/print}}</ref>
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 [[Rhythm Method#Reasons for high failure rate|long been recognized]].
Recently, hormonal assay has been suggested as a more accurate method of estimating fertility for EC studies.<!--
 --><ref name="espinosa 1999">{{cite journal |author=Espinos JJ, Rodriguez-Espinosa J, Senosiain R, Aura M, Vanrell C, Gispert M, Vega C, Calaf J |year=1999 |title=The role of matching menstrual data with hormonal measurements in evaluating effectiveness of postcoital contraception |journal=Contraception |volume=60 |issue=4 |pages=243-7 |id=PMID 10640171}}</ref>

===Safety===
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 [[indication (medicine)|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]] ''Medical Eligibility Criteria for Contraceptive Use'' list no medical condition for which the risks of emergency contraceptive pills (using progestin-only or combined oral contraceptive pills) outweigh the benefits, specifically noting [[breastfeeding]] and history of [[ectopic pregnancy]] as conditions where there are no restrictions on use of ECPs, and history of severe [[cardiovascular disease]] ([[myocardial infarction|heart attack]], [[stroke]], [[thrombus|blood clots]]), [[Angina pectoris|angina]], [[migraine]], and severe [[liver disease]] (including [[jaundice]]) as conditions where the advantages of using emergency contraceptive pills generally outweigh the theoretical or proven risks. The [[American Academy of Pediatrics]] (AAP) and experts on emergency contraception say 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]], the WHO, the [[Royal College of Obstetricians and Gynaecologists]]'s Faculty of Family Planning & Reproductive Health Care (FFPRHC) and other experts on emergency contraception state that there are no medical conditions in which progestin-only ECPs are contraindicated.
The FFPRHC ''UK Medical Eligibility Criteria for Contraceptive Use'' specifically note current [[venous thrombosis|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.
The herbal preparation of [[St John's wort]] and some [[enzyme induction|enzyme-inducing]] drugs (e.g. [[anticonvulsant]]s or [[rifampicin]]) may reduce the effectiveness of ECP, and a larger dose may be required.
The AAP, ACOG, FDA, WHO, FFPRHC and experts on emergency contraception say 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 trial]]s, indicates there is no increase in the relative risk of ectopic pregnancy in women who become pregnant after using progestin-only ECPs.

===Side Effects===
*The most common side effect of emergency contraceptive pills is [[nausea]] (50% of users of combined pills, 23% of progestin-only users), and a significant number of users [[vomit]]. Estrogen in combined ECPs is responsible for the increased incidence of nausea and vomiting. [[Antiemetic]]s may be prescribed for both methods, to be taken 1 hour before each ECP dose. If vomiting occurs within an hour after taking ECP's, it may be necessary to repeat the dose.

*Other common side effects are [[abdominal pain]], [[fatigue (physical)|fatigue]], [[headache]], [[dizziness]], and [[mastalgia|breast tenderness]]. These side effects normally resolve within 24 hours.

*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#Progestogen withdrawal bleeding|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.<!--
 --><ref name="bleeding patterns">{{cite journal |author=Raymond E, Goldberg A, Trussell J, Hays M, Roach E, Taylor D |title=Bleeding patterns after use of levonorgestrel emergency contraceptive pills |journal=Contraception |volume=73 |issue=4 |pages=376-81 |year=2006 |pmid=16531171}}</ref>  If levonorgestrel is taken after ovulation, it may increase the length of the [[luteal phase]], thus delaying menstruation by a few days.<!--
 --><ref>{{cite journal |author=Gainer E, Kenfack B, Mboudou E, Doh A, Bouyer J |title=Menstrual bleeding patterns following levonorgestrel emergency contraception |journal=Contraception |volume=74 |issue=2 |pages=118-24 |year=2006 |pmid=16860049}}</ref>  Mifepristone, if taken before ovulation, may delay ovulation by 3-4 days.<!--
 --><ref>{{cite journal |author=Gemzell-Danielsson K, Marions L |title=Mechanisms of action of mifepristone and levonorgestrel when used for emergency contraception |journal=Hum Reprod Update |volume=10 |issue=4 |pages=341-8 |year=2004 |pmid=15192056}}</ref>  (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.<ref name="bleeding patterns" />  If a woman's menstrual period is delayed by a week or more, it is advised that she take a [[pregnancy test]].<!--
 --><ref>{{cite journal |author= |title=ACOG Practice Bulletin. Clinical Management Guidelines for Obstetrician-Gynecologists, Number 69, December 2005. Emergency contraception |journal=Obstet Gynecol |volume=106 |issue=6 |pages=1443-52 |year=2005 |pmid=16319278}}</ref> (Earlier testing may not give accurate results.)

===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.<!--
 --><ref name="beyond coca-cola">{{cite journal | last = Ellertson | first = Charlotte | title = History and Efficacy of Emergency Contraception: Beyond Coca-Cola | journal = Family Planning Perspectives | volume = 28 | issue = 2 | publisher = Guttmacher Institute | date = March/April 1996 | url = http://www.guttmacher.org/pubs/journals/2804496.html | accessdate = 2006-11-22 }}</ref>  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.<ref name="beyond coca-cola" /><!--
 --><ref>{{cite journal | author = Chernev T, Ivanov S, Dikov I, Stamenkova R | title = Prospective study of contraception with levonorgestrel. | journal = Plan Parent Eur | volume = 24 | issue = 2 | pages = 25 | year = 1995 | id = PMID 12290800}}</ref>
* 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).<!--
 --><ref name="princeton">{{cite web | title = Effectiveness of Emergency Contraceptives | work = The Emergency Contraception Website | publisher = [[Office of Population Research]] at [[Princeton University]] and the Association of Reproductive Health Professionals | date = November 2006 | url = http://ec.princeton.edu/questions/eceffect.html|accessdate = 2006-12-2 }}</ref> These failure rates would be higher than those of almost all other birth control methods, including the [[rhythm method]] and [[coitus interruptus|withdrawal]].
* Like all hormonal methods, postcoital high-dose progestin-only oral contraceptive pills do not protect against [[sexually transmitted infection]]s.<ref name="princeton2">{{cite web | title = What is Emergency Contraception? | work = The Emergency Contraception Website|publisher = Office of Population Research at [[Princeton University]] and the Association of Reproductive Health Professionals | date = November 2006 | url = http://ec.princeton.edu/emergency-contraception.html | accessdate = 2006-12-2 }}</ref>

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&mdash;for example, if a woman has forgotten to take a birth control pill or when a [[condom]] is torn during sex.<ref name="princeton" />

==References==
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