Editing Ectopic pregnancy (section)

== Causes ==

There are several risk factors for ectopic pregnancies. However, in as many as one-third<ref name="pmid16099295">{{Cite journal |vauthors=Farquhar CM |year=2005 |title=Ectopic pregnancy |journal=Lancet |volume=366 |issue=9485 |pages=583–91 |doi=10.1016/S0140-6736(05)67103-6 |pmid=16099295 |s2cid=26445888}}</ref> to one-half<ref name="pmid18232175">{{Cite journal |vauthors=Majhi AK, Roy N, Karmakar KS, Banerjee PK |date=June 2007 |title=Ectopic pregnancy--an analysis of 180 cases |journal=Journal of the Indian Medical Association |volume=105 |issue=6 |pages=308, 310, 312 passim |pmid=18232175}}</ref> no risk factors can be identified. Risk factors include: [[pelvic inflammatory disease]], infertility, use of an [[intrauterine device]] (IUD), previous exposure to [[diethylstilbestrol]] (DES), tubal surgery, intrauterine surgery (e.g. [[Dilation and curettage|D&C]]), [[smoking]], previous ectopic pregnancy, [[endometriosis]], and [[tubal ligation]].<ref>{{Cite web |title=BestBets: Risk Factors for Ectopic Pregnancy |url=http://www.bestbets.org/bets/bet.php?id=921 |url-status=live |archive-url=https://web.archive.org/web/20081219012137/http://www.bestbets.org/bets/bet.php?id=921 |archive-date=2008-12-19}}</ref><ref>{{Cite journal |display-authors=6 |vauthors=Rana P, Kazmi I, Singh R, Afzal M, Al-Abbasi FA, Aseeri A, Singh R, Khan R, Anwar F |date=October 2013 |title=Ectopic pregnancy: a review |journal=Archives of Gynecology and Obstetrics |volume=288 |issue=4 |pages=747–57 |doi=10.1007/s00404-013-2929-2 |pmid=23793551 |s2cid=42807796}}</ref> A previous induced [[abortion]] does not appear to increase the risk.<ref>{{Cite book |title=Management of Unintended and Abnormal Pregnancy: Comprehensive Abortion Care |date=2011 |publisher=John Wiley & Sons |isbn=9781444358476 |chapter=16 Answering questions about long term outcomes |chapter-url=https://books.google.com/books?id=iK7xrRr2p9sC&pg=RA1-PT376 |archive-url=https://web.archive.org/web/20170910181336/https://books.google.com/books?id=iK7xrRr2p9sC&pg=RA1-PT376 |archive-date=2017-09-10 |url-status=live}}</ref> The IUD does not increase the risk of ectopic pregnancy, but with an IUD if pregnancy occurs it is more likely to be ectopic than intrauterine.<ref name="Tubal ectopic pregnancy">{{Cite journal |vauthors=Kumar V, Gupta J |date=November 2015 |title=Tubal ectopic pregnancy |journal=BMJ Clinical Evidence |volume=2015 |pmc=4646159 |pmid=26571203}}</ref> The risk of ectopic pregnancy after chlamydia infection is low.<ref>{{Cite journal |vauthors=Bakken IJ |date=February 2008 |title=Chlamydia trachomatis and ectopic pregnancy: recent epidemiological findings |journal=Current Opinion in Infectious Diseases |volume=21 |issue=1 |pages=77–82 |doi=10.1097/QCO.0b013e3282f3d972 |pmid=18192790 |s2cid=30584041}}</ref> The exact mechanism through which chlamydia increases the risk of ectopic pregnancy is uncertain, though some research suggests that the infection can affect the structure of fallopian tubes.<ref>{{Cite journal |vauthors=Sivalingam VN, Duncan WC, Kirk E, Shephard LA, Horne AW |date=October 2011 |title=Diagnosis and management of ectopic pregnancy |journal=The Journal of Family Planning and Reproductive Health Care |volume=37 |issue=4 |pages=231–40 |doi=10.1136/jfprhc-2011-0073 |pmc=3213855 |pmid=21727242}}</ref>

{| class="wikitable"
|+Risk factors <ref>{{Cite journal |vauthors=Marion LL, Meeks GR |date=June 2012 |title=Ectopic pregnancy: History, incidence, epidemiology, and risk factors |journal=Clinical Obstetrics and Gynecology |volume=55 |issue=2 |pages=376–86 |doi=10.1097/GRF.0b013e3182516d7b |pmid=22510618}}</ref><ref name="ESHRE2015" />
! colspan="2" |Relative risk factors
|-
|High
|Tubal sterilization, IUD, prior ectopic, PID (pelvic inflammatory disease), endometriosis, SIN (salpingitis isthmica nodosa)
|-
|Moderate
|Smoking, having more than 1 partner, infertility, chlamydia
|-
|Low
|Douching, age greater than 35, age less than 18, GIFT (gamete intrafallopian transfer)
|}

=== Tube damage ===
[[File:EUG 2.png|thumb|Left fallopian tube with an ectopic pregnancy in a 25-year-old woman after a [[salpingectomy]]]]
Tubal pregnancy is when the egg is [[Implantation (embryology)|implanted]] in the fallopian tubes. Hair-like [[Cilium|cilia]] located on the internal surface of the fallopian tubes carry the fertilized egg to the uterus. Fallopian cilia are sometimes seen in reduced numbers after an ectopic pregnancy, leading to a hypothesis that cilia damage in the fallopian tubes is likely to lead to an ectopic pregnancy.<ref name="Lyons">{{Cite journal |vauthors=Lyons RA, Saridogan E, Djahanbakhch O |year=2006 |title=The reproductive significance of human Fallopian tube cilia |journal=Human Reproduction Update |volume=12 |issue=4 |pages=363–72 |doi=10.1093/humupd/dml012 |pmid=16565155 |doi-access=free}}</ref> Women who smoke have a higher chance of an ectopic pregnancy in the fallopian tubes. Smoking leads to risk factors of damaging and destroying cilia.<ref name="Lyons" /> As cilia degenerate, the amount of time it takes for the fertilized egg to reach the uterus will increase. The fertilized egg, if it does not reach the uterus in time, will hatch from the non-adhesive [[zona pellucida]] and implant itself inside the fallopian tube, thus causing ectopic pregnancy.{{cn|date=September 2024}}

Women with pelvic inflammatory disease (PID) have a high occurrence of ectopic pregnancy.<ref name="Tay">{{Cite journal |vauthors=Tay JI, Moore J, Walker JJ |date=August 2000 |title=Ectopic pregnancy |journal=The Western Journal of Medicine |volume=173 |issue=2 |pages=131–4 |doi=10.1136/ewjm.173.2.131 |pmc=1071024 |pmid=10924442}}</ref> This results from the build-up of [[scar|scar tissue]] in the fallopian tubes, causing damage to the cilia.<ref name=speroff/> However, if both tubes were completely blocked, so that sperm and egg were physically unable to meet, then fertilization of the egg would naturally be impossible, and neither normal pregnancy nor ectopic pregnancy could occur. Intrauterine adhesions (IUA) present in [[Asherman's syndrome]] can cause ectopic cervical pregnancy or, if adhesions partially block access to the tubes via the [[Ostium of Fallopian tube|ostia]], ectopic tubal pregnancy.<ref name="Schenker">{{Cite journal |vauthors=Schenker JG, Margalioth EJ |date=May 1982 |title=Intrauterine adhesions: an updated appraisal |journal=Fertility and Sterility |volume=37 |issue=5 |pages=593–610 |doi=10.1016/S0015-0282(16)46268-0 |pmid=6281085 |doi-access=free}}</ref><ref name="Klyszejko">{{Cite journal |vauthors=Kłyszejko C, Bogucki J, Kłyszejko D, Ilnicki W, Donotek S, Koźma J |date=January 1987 |title=[Cervical pregnancy in Asherman's syndrome] |journal=Ginekologia Polska |volume=58 |issue=1 |pages=46–8 |pmid=3583040}}</ref><ref name="Dicker:">{{Cite journal |vauthors=Dicker D, Feldberg D, Samuel N, Goldman JA |date=January 1985 |title=Etiology of cervical pregnancy. Association with abortion, pelvic pathology, IUDs and Asherman's syndrome |journal=The Journal of Reproductive Medicine |volume=30 |issue=1 |pages=25–7 |pmid=4038744}}</ref> Asherman's syndrome usually occurs from intrauterine surgery, most commonly after [[Dilation and curettage|D&C]].<ref name="Schenker" />  Endometrial/pelvic/genital [[tuberculosis]], another cause of Asherman's syndrome, can also lead to ectopic pregnancy as infection may lead to tubal adhesions in addition to intrauterine adhesions.<ref name="Bukulmez">{{Cite journal |vauthors=Bukulmez O, Yarali H, Gurgan T |date=August 1999 |title=Total corporal synechiae due to tuberculosis carry a very poor prognosis following hysteroscopic synechialysis |journal=Human Reproduction |volume=14 |issue=8 |pages=1960–1 |doi=10.1093/humrep/14.8.1960 |pmid=10438408 |doi-access=free}}</ref>

Tubal ligation can predispose to ectopic pregnancy. Reversal of tubal sterilization ([[tubal reversal]]) carries a risk for ectopic pregnancy. This is higher if more destructive methods of tubal ligation (tubal cautery, partial removal of the tubes) have been used than less destructive methods (tubal clipping). A history of a tubal pregnancy increases the risk of future occurrences to about 10%.<ref name=speroff/> This risk is not reduced by removing the affected tube, even if the other tube appears normal. The best method for diagnosing this is to do an early ultrasound.{{cn|date=September 2024}}

=== Endometriosis ===
{{Main|Endometriosis}}

Endometriosis is a disease in which cells similar to those of the [[endometrium]], the tissue covering the inside of the uterus, grow outside the uterus.  An embryo attaching to such lesions leads to an ectopic pregnancy. The results of a 30-year study of reproductive and pregnancy outcomes, involving 14,000+ women of child-bearing age, were presented at the 2015 [[European Society of Human Reproduction and Embryology]] (ESHRE) annual congress.<ref name="ESHRE2015">{{Cite web |last=Saraswat |first=Lucky |date=2015 |title=ESHRE2015: Endometriosis associated with a greater risk of complications in pregnancy |url=https://endometriosis.org/news/congress-highlights/eshre2015-endometriosis-associated-with-a-greater-risk-of-complications-in-pregnancy/#:~:text=After%20adjustments%20for%20age%20and%20previous%20pregnancy%2C%20results,three%20times%20higher%20for%20ectopic%20pregnancy%20%28OR%202.7%29 |access-date=14 February 2024 |website=endometriosis.org |publisher=European Society of Human Reproduction and Embryology}}</ref> 39% of the study group had surgically confirmed endometriosis. Compared to their peers, the endometriosis subgroup had a 76% higher risk for miscarriage and a 270% higher risk for ectopic pregnancy. The higher endometriosis risks were attributed to increased pelvic inflammation and structural and functional changes in the uterine lining.{{cn|date=September 2024}}

=== Other ===

Although some investigations have shown that patients may be at higher risk for ectopic pregnancy with advancing age, it is believed that age is a variable that could act as a surrogate for other risk factors. Vaginal douching is thought by some to increase ectopic pregnancies.<ref name=speroff/> Women exposed to [[diethylstilbestrol|DES]] in utero (also known as "DES daughters") also have an elevated risk of ectopic pregnancy.<ref name="Schrager2004">{{Cite journal |vauthors=Schrager S, Potter BE |date=May 2004 |title=Diethylstilbestrol exposure |url=http://www.aafp.org/afp/2004/0515/p2395.html |url-status=live |journal=American Family Physician |volume=69 |issue=10 |pages=2395–400 |pmid=15168959 |archive-url=https://web.archive.org/web/20150402101957/http://www.aafp.org/afp/2004/0515/p2395.html |archive-date=2015-04-02}}</ref> However, DES has not been used since 1971 in the United States.<ref name=Schrager2004/> It has also been suggested that pathologic generation of [[nitric oxide]] through increased [[iNOS]] production may decrease [[Fallopian tube|tubal ciliary]] beats and smooth muscle contractions and thus affect embryo transport, which may consequently result in ectopic pregnancy.<ref>{{Cite journal |vauthors=Al-Azemi M, Refaat B, Amer S, Ola B, Chapman N, Ledger W |date=August 2010 |title=The expression of inducible nitric oxide synthase in the human fallopian tube during the menstrual cycle and in ectopic pregnancy |journal=Fertility and Sterility |volume=94 |issue=3 |pages=833–40 |doi=10.1016/j.fertnstert.2009.04.020 |pmid=19482272}}</ref> Low socioeconomic status may also be a risk factor for ectopic pregnancy.<ref name="pmid23726169">{{Cite journal |vauthors=Yuk JS, Kim YJ, Hur JY, Shin JH |date=August 2013 |title=Association between socioeconomic status and ectopic pregnancy rate in the Republic of Korea |journal=International Journal of Gynaecology and Obstetrics |volume=122 |issue=2 |pages=104–7 |doi=10.1016/j.ijgo.2013.03.015 |pmid=23726169 |s2cid=25547683}}</ref>