Editing Recurrent miscarriage (section)

=== Immune factors ===

A common feature of immune factors in causing recurrent pregnancy loss appears to be a decreased [[maternal immune tolerance]] towards the fetus.<ref>{{cite journal | vauthors = Williams Z | title = Inducing tolerance to pregnancy | journal = The New England Journal of Medicine | volume = 367 | issue = 12 | pages = 1159–1161 | date = September 2012 | pmid = 22992082 | pmc = 3644969 | doi = 10.1056/NEJMcibr1207279 }}</ref>

* '''Antiphospholipid syndrome:''' The [[antiphospholipid syndrome]] is an autoimmune disease that is a common cause of recurrent pregnancy loss.<ref name="RCOG-recurrent">{{cite web|last=Royal College of Obstetricians and Gynaecologists (RCOG)|title=The investigation and treatment of couples with recurrent first-trimester and second-trimester miscarriage|url=http://www.rcog.org.uk/files/rcog-corp/GTG17recurrentmiscarriage.pdf|work=Green-top Guideline No. 17|publisher=Royal College of Obstetricians and Gynaecologists (RCOG)|access-date=2 July 2013|date=April 2011|url-status=dead|archive-url=https://web.archive.org/web/20130705172612/http://www.rcog.org.uk/files/rcog-corp/GTG17recurrentmiscarriage.pdf|archive-date=5 July 2013}}</ref><ref name="ACOG2001" /> Around 15% of the women who have recurrent miscarriages have high levels of antiphospholipid antibodies.<ref name="RCOG-recurrent" /> Women who have had more than one miscarriage in the first trimester, or a miscarriage in the second trimester, may have their blood tested for antibodies, to determine if they have antiphospholipid syndrome.<ref name="RCOG-recurrent" /> Women diagnosed with antiphospholipid syndrome generally take aspirin or heparin in subsequent pregnancies, but questions remain due to the lack of high quality trials.<ref name="Empson-CC">{{cite journal | vauthors = Empson M, Lassere M, Craig J, Scott J | title = Prevention of recurrent miscarriage for women with antiphospholipid antibody or lupus anticoagulant | journal = The Cochrane Database of Systematic Reviews | volume = 2005 | issue = 2 | pages = CD002859 | date = April 2005 | pmid = 15846641 | pmc = 6768987 | doi = 10.1002/14651858.CD002859.pub2 }}</ref><ref>''Patient’s Fact Sheet: Recurrent Pregnancy Lost''. American Society for Reproductive Medicine, 8/2008</ref>
* '''Thyroid antibodies:''' [[Anti-thyroid autoantibodies]] are associated with an increased risk of recurrent miscarriage with an [[odds ratio]] of 2.3 with a 95% [[confidence interval]] of 1.5–3.5.<ref>{{cite journal | vauthors = van den Boogaard E, Vissenberg R, Land JA, van Wely M, van der Post JA, Goddijn M, Bisschop PH | title = Significance of (sub)clinical thyroid dysfunction and thyroid autoimmunity before conception and in early pregnancy: a systematic review | journal = Human Reproduction Update | volume = 17 | issue = 5 | pages = 605–619 | year = 2011 | pmid = 21622978 | doi = 10.1093/humupd/dmr024 | doi-access =  }}</ref>
* '''Increased uterine NK cells:''' [[Natural killer cell]]s, a type of white blood cell, are present in uterine tissue. High levels of these cells may be linked to RPL but high numbers or the presence of these cells is not a predictor of pregnancy loss in women who have not have had a miscarriage.<ref>{{cite book | last = Christiansen | first = Ole | name-list-style = vanc | title = Recurrent pregnancy loss | publisher = John Wiley & Sons | location = Chichester, West Sussex, UK | year = 2014 |pages=29–37| isbn = 9781118749180 }}</ref>
* '''Male-specific minor histocompatibility:''' Immunization of mothers against male-specific minor histocompatibility (H-Y) antigens has a pathogenic role in many cases of ''secondary recurrent miscarriage'', that is, recurrent miscarriage in pregnancies succeeding a previous live birth. An example of this effect is that the male:female ratio of children born prior and subsequent to secondary recurrent miscarriage is 1.49 and 0.76 respectively.<ref>{{cite journal | vauthors = Nielsen HS | title = Secondary recurrent miscarriage and H-Y immunity | journal = Human Reproduction Update | volume = 17 | issue = 4 | pages = 558–574 | year = 2011 | pmid = 21482560 | doi = 10.1093/humupd/dmr005 | doi-access = free }}</ref>