Editing Emergency contraception (section)

===Safety===
{{See also|Progestin#Side effects|Progestin#Mood changes}}

The most common side effect reported by users of emergency contraceptive pills was [[nausea]], reported by 14 to 23% of levonorgestrel-only users and 50.5% of Yuzpe regimen users. [[Vomiting]] is much less common and unusual with levonorgestrel-only ECPs (5.6% of levonorgestrel-only users vs 18.8% of 979 Yuzpe regimen users in 1998 WHO trial; 1.4% of 2,720 levonorgestrel-only users in the 2002 WHO trial).<ref name="WHO 1998"/><ref name="WHO 2002"/><ref name="FSRH EC 2012"/> [[Antiemetic|Anti-emetics]] are not routinely recommended with levonorgestrel-only ECPs.<ref name="FSRH EC 2012"/><ref name="WHO SPR 20">{{cite book|author=WHO Department of Reproductive Health and Research|date=December 31, 2004|chapter=Question 20. What can a woman do to prevent nausea and vomiting when taking emergency contraceptive pills (ECPs)?|title=Selected practice recommendations for contraceptive use|edition  =2nd|location=Geneva|publisher=World Health Organization|isbn=978-92-4-156284-3|archive-url=https://web.archive.org/web/20090113014114/http://www.who.int/reproductive-health/publications/spr/spr_q20_prevent_nausea_ecps.html|archive-date=2009-01-13|chapter-url=https://www.who.int/reproductive-health/publications/spr/spr_q20_prevent_nausea_ecps.html}}</ref> If a woman vomits within 2 hours of taking a levonorgestrel-only ECP, she should take a further dose as soon as possible.<ref name="FSRH EC 2012"/><ref name="WHO SPR 21">{{cite book|author=WHO Department of Reproductive Health and Research|date=December 31, 2004|chapter=Question 21. What can a woman do if she vomits after taking emergency contraceptive pills (ECPs)?|title=Selected practice recommendations for contraceptive use|edition  =2nd|location=Geneva |publisher=World Health Organization|isbn=978-92-4-156284-3|archive-url=https://web.archive.org/web/20090113042947/http://www.who.int/reproductive-health/publications/spr/spr_q21_womiting_ecps.html|archive-date=2009-01-13|chapter-url=https://www.who.int/reproductive-health/publications/spr/spr_q21_womiting_ecps.html}}</ref>

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 (physical)|fatigue]], [[headache]], [[dizziness]], and [[mastalgia|breast tenderness]].<ref name="WHO 1998"/><ref name="WHO 2002"/><ref name="FSRH EC 2012"/><ref>{{cite web | title = Morning-after pill | publisher = Mayo Clinic |url=https://www.mayoclinic.org/tests-procedures/morning-after-pill/about/pac-20394730 | access-date = 13 Sep 2020}}</ref> Side effects generally resolve within 24 hours,<ref name="Trussell 2014"/> although temporary disruption of the menstrual cycle is 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.<ref name="Raymond 2006">{{cite journal | vauthors = Raymond EG, 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 = 376–381 | date = April 2006 | pmid = 16531171 | doi = 10.1016/j.contraception.2005.10.006 }}</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 | vauthors = Gainer E, Kenfack B, Mboudou E, Doh AS, Bouyer J | title = Menstrual bleeding patterns following levonorgestrel emergency contraception | journal = Contraception | volume = 74 | issue = 2 | pages = 118–124 | date = August 2006 | pmid = 16860049 | pmc = 1934349 | doi = 10.1016/j.contraception.2006.02.009 }}</ref> Mifepristone, if taken before ovulation, may delay ovulation by 3–4 days<ref>{{cite journal | vauthors = Gemzell-Danielsson K, 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 = July–August 2004 | pmid = 15192056 | doi = 10.1093/humupd/dmh027 | doi-access = free }}</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="Raymond 2006" /> If a woman's menstrual period is delayed by two weeks or more, it is advised that she take a [[pregnancy test]].<ref name="ACOG 2010" /> (Earlier testing may not give accurate results.)

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.<ref name="Trussell 2014"/><ref name="AAP 2005">{{cite journal | vauthors = ((American Academy of Pediatrics Committee on Adolescence)) | title = Emergency contraception | journal = Pediatrics | volume = 116 | issue = 4 | pages = 1026–1035 | date = October 2005 | pmid = 16147972 | pmc = 1197142 | doi = 10.1542/peds.2005-1877 }}</ref><ref name="Grimes 2002">{{cite journal | vauthors = Grimes DA, Raymond EG | title = Emergency contraception | journal = Annals of Internal Medicine | volume = 137 | issue = 3 | pages = 180–189 | date = August 2002 | pmid = 12160366 | doi = 10.7326/0003-4819-137-3-200208060-00010 | s2cid = 19236983 }}</ref><ref name="ACOG 2010">{{cite journal | vauthors = ((American College of Obstetricians and Gynecologists)) | title = ACOG Practice Bulletin No. 112: Emergency contraception | journal = Obstetrics and Gynecology | volume = 115 | issue = 5 | pages = 1100–1109 | date = May 2010 | pmid = 20410799 | doi = 10.1097/AOG.0b013e3181deff2a | doi-access = free }}</ref><ref name="FDA Plan B Rx to OTC switch med review">{{cite web|author=FDA Center for Drug Evaluation and Research|date=August 22, 2006|title=Plan B Rx to OTC switch Medical Reviews|location=Beltsville, Md.|publisher=Food and Drug Administration|pages=32–7, 133–77|url=http://www.accessdata.fda.gov/drugsatfda_docs/nda/2006/021045s011_Plan_B__MedR.pdf|access-date=2006-12-13}}</ref><ref name="WHO MEC 2009">{{cite book|author=WHO Department of Reproductive Health and Research|year=2009|chapter=Emergency contraceptive pills (ECPs)|title=Medical eligibility criteria for contraceptive use|edition  =4th|location=Geneva|publisher=World Health Organization|isbn=978-92-4-156388-8|page=63|chapter-url=http://whqlibdoc.who.int/publications/2010/9789241563888_eng.pdf}}</ref><ref name="UK MEC 2009">{{cite web|author1=RCOG Faculty of Sexual|author2=Reproductive Healthcare|year=2009|title=UK medical eligibility criteria for contraceptive use: Emergency contraception|location=London|publisher=Royal College of Obstetricians and Gynaecologists|pages=107–115|url=http://www.fsrh.org/pdfs/UKMEC2009.pdf|access-date=2012-04-30|archive-date=2016-03-03|archive-url=https://web.archive.org/web/20160303222644/http://www.fsrh.org/pdfs/UKMEC2009.pdf|url-status=dead}}</ref><ref name="US MEC 2010">{{cite journal | vauthors = ((CDC Division of Reproductive Health)) | title = U S. Medical Eligibility Criteria for Contraceptive Use, 2010 | journal = MMWR. Recommendations and Reports | volume = 59 | issue = RR-4 | pages = 1–86 | date = June 2010 | pmid = 20559203 |url=https://www.cdc.gov/mmwr/pdf/rr/rr5904.pdf }}</ref><ref name="Davidoff 2006">{{cite journal | vauthors = Davidoff F, Trussell J | title = Plan B and the politics of doubt | journal = JAMA | volume = 296 | issue = 14 | pages = 1775–1778 | date = October 2006 | pmid = 17032991 | doi = 10.1001/jama.296.14.1775 }}</ref>

The [[World Health Organization]] (WHO) lists no medical condition for which the risks of emergency contraceptive pills outweigh the benefits.<ref name="WHO MEC 2009"/> The [[American Academy of Pediatrics]] (AAP) and experts on emergency contraception have concluded that progestin-only ECPs are preferable to combined ECPs containing estrogen for all women, and particularly those with a history of blood clots, stroke, or migraine.<ref name="Trussell 2014"/><ref name="AAP 2005"/><ref name="Grimes 2002"/>

There are no medical conditions in which progestin-only ECPs are contraindicated.<ref name="Trussell 2014"/><ref name="AAP 2005"/><ref name="Grimes 2002"/><ref name="ACOG 2010"/><ref name="FDA Plan B Rx to OTC switch med review"/><ref name="WHO MEC 2009"/><ref name="UK MEC 2009"/> Current [[venous thrombosis|venous thromboembolism]], current or history of [[breast cancer]], [[inflammatory bowel disease]], and [[acute intermittent porphyria]] are conditions where the advantages of using emergency contraceptive pills generally outweigh the theoretical or proven risks.<ref name="UK MEC 2009"/>

ECPs, like all other contraceptives, reduce the absolute risk of [[ectopic pregnancy]] by preventing pregnancies and there is no increase in the relative risk of ectopic pregnancy in women who become pregnant after using progestin-only ECPs.<ref name="Trussell 2014"/><ref name="WHO 2010">{{cite web|author=UNDP/UNFPA/WHO/World Bank Special Programme of Research, Development and Research Training in Human Reproduction (HRP)|date=March 25, 2010|title=Fact sheet on the safety of levonorgestrel-alone emergency contraceptive pills (LNG ECPs)|location=Geneva|publisher=World Health Organization|url=http://whqlibdoc.who.int/hq/2010/WHO_RHR_HRP_10.06_eng.pdf}}{{blockquote|Can LNG ECPs cause an abortion?<br />LNG ECPs do not interrupt an established pregnancy or harm a developing embryo.<sup>15</sup> The evidence available to date shows that LNG ECP use does not prevent a fertilized egg from attaching to the uterine lining. The primary mechanism of action is to stop or disrupt ovulation; LNG ECP use may also prevent the sperm and egg from meeting.<sup>16</sup>}}</ref><ref name="Cleland 2010">{{cite journal | vauthors = Cleland K, Raymond E, Trussell J, Cheng L, Zhu H | title = Ectopic pregnancy and emergency contraceptive pills: a systematic review | journal = Obstetrics and Gynecology | volume = 115 | issue = 6 | pages = 1263–1266 | date = June 2010 | pmid = 20502299 | pmc = 3903002 | doi = 10.1097/AOG.0b013e3181dd22ef }}</ref>