Editing Miscarriage (section)

===Pre-existing diseases===
Several [[pre-existing diseases in pregnancy]] can potentially increase the risk of miscarriage, including [[Diabetes mellitus|diabetes]], [[endometriosis]], [[polycystic ovary syndrome]] (PCOS), [[hypothyroidism]], certain infectious diseases, and autoimmune diseases. 
Women with endometriosis report a 76%<ref name="ESHRE2015">{{cite web |last1=Saraswat |first1=Lucky |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 |website=endometriosis.org |publisher=European Society of Human Reproduction and Embryology |access-date=14 February 2024 |date=2015}}</ref> to 298%<ref name="PMC9588543">{{cite journal |last1=Schliep |first1=Karen C |last2=Farland |first2=Leslie V |last3=Pollack |first3=Anna Z |last4=Louis |first4=Germaine Buck |last5=Stanford |first5=Joseph B |last6=Allen-Brady |first6=Kristina |last7=Varner |first7=Michael W |last8=Kah |first8=Kebba |last9=Peterson |first9=C Matthew |title=Endometriosis diagnosis, staging and typology and adverse pregnancy outcome history |journal=Paediatric and Perinatal Epidemiology |date=November 2022 |volume=36 |issue=6 |pages=771–781 |doi=10.1111/ppe.12887 |pmid=35570746 |pmc=9588543}}</ref> increase in miscarriages versus their non-afflicted peers, the range affected by the [[Endometriosis#Stages of disease|severity of their disease]]. PCOS may increase the risk of miscarriage.<ref name="NHS-Miscarriage-Causes"/> Two studies suggested treatment with the drug [[metformin]] significantly lowers the rate of miscarriage in women with PCOS,<ref name=metformin>{{cite journal | vauthors = Jakubowicz DJ, Iuorno MJ, Jakubowicz S, Roberts KA, Nestler JE | title = Effects of metformin on early pregnancy loss in the polycystic ovary syndrome | journal = The Journal of Clinical Endocrinology and Metabolism | volume = 87 | issue = 2 | pages = 524–9 | date = February 2002 | pmid = 11836280 | doi = 10.1210/jcem.87.2.8207 | doi-access = free }}</ref><ref name=Khattab>{{cite journal | vauthors = Khattab S, Mohsen IA, Foutouh IA, Ramadan A, Moaz M, Al-Inany H | title = Metformin reduces abortion in pregnant women with polycystic ovary syndrome | journal = Gynecological Endocrinology | volume = 22 | issue = 12 | pages = 680–4 | date = December 2006 | pmid = 17162710 | doi = 10.1080/09513590601010508 | s2cid = 41735428 }}</ref> but the quality of these studies has been questioned.<ref name="RCOG-PCOS">{{cite web|last=Royal College of Obstetricians and Gynaecologists|title=Long-term consequences of polycystic ovarian syndrome|url=http://www.rcog.org.uk/files/rcog-corp/uploaded-files/GT33_LongTermPCOS.pdf|archive-url=https://web.archive.org/web/20090413130238/http://www.rcog.org.uk/files/rcog-corp/uploaded-files/GT33_LongTermPCOS.pdf|url-status=dead|archive-date=2009-04-13|website=Green-top Guideline No. 27|publisher=Royal College of Obstetricians and Gynaecologists|access-date=2 July 2013|date=December 2007}}</ref> Metformin treatment in pregnancy is not safe.<ref name=Acta>{{cite journal | vauthors = Lilja AE, Mathiesen ER | title = Polycystic ovary syndrome and metformin in pregnancy | journal = Acta Obstetricia et Gynecologica Scandinavica | volume = 85 | issue = 7 | pages = 861–8 | year = 2006 | pmid = 16817087 | doi = 10.1080/00016340600780441 | s2cid = 42002774 | doi-access = free }}</ref> In 2007, the Royal College of Obstetricians and Gynaecologists also recommended against the use of the drug to prevent miscarriage.<ref name="RCOG-PCOS" /> [[Thrombophilia]]s or defects in coagulation and bleeding were once thought to be a risk of miscarriage but have been subsequently questioned.{{sfn|Hoffman|page=174}} Severe cases of hypothyroidism increase the risk of miscarriage. The effect of milder cases of hypothyroidism on miscarriage rates has not been established. A condition called luteal phase defect (LPD) is a failure of the uterine lining to be fully prepared for pregnancy. This can keep a fertilised egg from implanting or result in miscarriage.<ref>{{cite web|url=https://www.womenshealth.gov/pregnancy/you-get-pregnant/trying-conceive/#4|title=Trying to conceive {{!}} womenshealth.gov|website=womenshealth.gov|access-date=2017-09-11|date=December 13, 2016}}{{PD-notice}}</ref>

''[[Mycoplasma genitalium]]'' infection is associated with an increased risk of [[preterm birth]] and miscarriage.<ref name="LisRowhani-Rahbar2015"/>

Infections can increase the risk of a miscarriage: rubella (German measles), cytomegalovirus, bacterial vaginosis, [[HIV]], chlamydia, gonorrhoea, syphilis, and malaria.<ref name="NHS-Miscarriage-Causes"/>