Editing Miscarriage (section)

===Classification===
A threatened miscarriage is any bleeding during the first half of pregnancy.<ref name=Relationship /> At the investigation, it may be found that the foetus remains viable and the pregnancy continues without further problems.{{Medical citation needed|date=November 2017}}

An [[Anembryonic gestation|anembryonic pregnancy]] (also called an "empty sac" or "blighted ovum") is a condition where the [[gestational sac]] develops normally, while the embryonic part of the pregnancy is either absent or stops growing very early. This accounts for approximately half of miscarriages. All other miscarriages are classified as embryonic miscarriages, meaning that there is an embryo present in the gestational sac. Half of embryonic miscarriages have [[aneuploidy]] (an abnormal number of [[chromosome]]s).<ref name=Will2013 />

An inevitable miscarriage occurs when the cervix has already dilated,<ref name="isbn 0-07-144874-8">{{cite book |first1=Latha |last1=Stead |first2=S. Matthew |last2=Stead |first3=Matthew |last3=Kaufman|first4=Luis |last4=Suarez |title=First Aid for The Obstetrics and Gynecology Clerkship |url=https://archive.org/details/maxwellquickmedi00stea |url-access=limited |publisher=McGraw-Hill|location=New York |year=2006 |page=[https://archive.org/details/maxwellquickmedi00stea/page/n136 138] |isbn=978-0-07-144874-1}}</ref> but the foetus has yet to be expelled. This usually will progress to a complete miscarriage. The foetus may or may not have cardiac activity.

[[File:Complete miscarriage.jpg|thumb|left|[[Transvaginal ultrasonography]] after an episode of heavy bleeding in an intrauterine pregnancy that had been confirmed by previous ultrasonography. There is some widening between the [[uterine wall]]s, but no sign of any [[gestational sac]], thus, in this case, being diagnostic of a complete miscarriage.]] A complete miscarriage is when all products of conception have been expelled; these may include the [[trophoblast]], [[chorionic villi]], [[gestational sac]], [[yolk sac]], and [[fetal pole]] ([[embryo]]); or later in the pregnancy the [[fetus|foetus]], [[umbilical cord]], [[placenta]], amniotic fluid, and [[amniotic sac|amniotic membrane]]. The presence of a [[pregnancy test]] that is still positive, as well as an empty uterus upon [[transvaginal ultrasonography]], does, however, fulfil the definition of [[pregnancy of unknown location]]. Therefore, there may be a need for follow-up pregnancy tests to ensure that there is no remaining pregnancy, including ectopic pregnancy.{{Citation needed|date=May 2019}}
[[File:Incomplete miscarriage.jpg|thumb|[[Transvaginal ultrasonography]], with some products of conception in the [[cervix]] (to the left in the image) and remnants of a [[gestational sac]] by the [[fundus of the uterus|fundus]] (to the right in the image), indicating an incomplete miscarriage]]

An incomplete miscarriage occurs when some [[products of conception]] have been passed, but some remain inside the uterus.<ref name="MedlinePlus">{{cite web |author=MedlinePlus | author-link =MedlinePlus | date = October 25, 2004 |url=https://www.nlm.nih.gov/medlineplus/ency/article/000904.htm | title =Abortion – incomplete | website=Medical Encyclopedia| access-date =May 24, 2006 |archive-url =https://web.archive.org/web/20060425090648/https://www.nlm.nih.gov/medlineplus/ency/article/000904.htm <!-- Bot retrieved archive --> |archive-date = April 25, 2006}}</ref> However, an increased distance between the [[uterine wall]]s on transvaginal ultrasonography may also simply be an increased endometrial thickness and/or a [[polyp (medicine)|polyp]]. The use of a Doppler ultrasound may be better in confirming the presence of significant retained products of conception in the uterine cavity.<ref name="kirk2013">{{cite journal | vauthors = Kirk E, Bottomley C, Bourne T | title = Diagnosing ectopic pregnancy and current concepts in the management of pregnancy of unknown location | journal = Human Reproduction Update | volume = 20 | issue = 2 | pages = 250–61 | year = 2013 | pmid = 24101604 | doi = 10.1093/humupd/dmt047 | doi-access =  }}</ref> In cases of uncertainty, [[ectopic pregnancy]] must be excluded using techniques like serial [[beta-hCG]] measurements.<ref name="kirk2013" />[[File:Delayed or missed miscarriage at 13 weeks.gif|thumb|left|160px|A 13-week fetus without cardiac activity located in the uterus (delayed or missed miscarriage)]]A missed miscarriage is when the embryo or fetus has died, but a miscarriage has not yet occurred. It is also referred to as delayed miscarriage, silent miscarriage, or missed abortion.<ref name="Farquharson">{{cite journal |author4=ESHRE Special Interest Group for Early Pregnancy |vauthors=Farquharson RG, Jauniaux E, Exalto N |date=November 2005 |title=Updated and revised nomenclature for description of early pregnancy events |journal=Human Reproduction |volume=20 |issue=11 |pages=3008–11 |doi=10.1093/humrep/dei167 |pmid=16006453 |doi-access=free}}</ref><ref name="Hutchon-1997">{{cite journal | vauthors = Hutchon DJ | title = Missed abortion versus delayed miscarriage | journal = British Journal of Obstetrics and Gynaecology | volume = 104 | issue = 6 | pages = 753 | date = June 1997 | pmid = 9197887 | doi = 10.1111/j.1471-0528.1997.tb11994.x | s2cid = 27778591 | doi-access =  }}</ref>

A [[Septic abortion|septic miscarriage]] occurs when the tissue from a missed or incomplete miscarriage becomes infected, which carries the risk of spreading infection ([[sepsis]]) and can be fatal.<ref name=Will2013 />

[[Recurrent miscarriage]] ("recurrent pregnancy loss" (RPL), "recurrent spontaneous abortion (RSA), or "habitual abortion") is the occurrence of multiple consecutive miscarriages; the exact number used to diagnose recurrent miscarriage varies; however, two is the minimum threshold to meet the criteria.<ref>{{cite journal |last1=Paz Levy |first1=Dorit |last2=Wainstock |first2=Tamar |last3=Sheiner |first3=Eyal |last4=Sergienko |first4=Ruslan |last5=Landau |first5=Daniella |last6=Walfisch |first6=Asnat |date=2019-01-01 |title=Maternal recurrent pregnancy loss is associated with an increased risk for long-term neurological morbidity in offspring |journal=Developmental Medicine & Child Neurology |language=en |volume=61 |issue=1 |pages=91–97 |doi=10.1111/dmcn.13976 |pmid=30058166 |s2cid=51863388 |issn=0012-1622|doi-access=free }}</ref><ref name=Will2013 /><ref name="jidc.org"/> If the proportion of pregnancies ending in miscarriage is 15% and assuming that miscarriages are independent events,<ref name="rcog2003" /> then the probability of two consecutive miscarriages is 2.25% and the probability of three consecutive miscarriages is 0.34%. The occurrence of recurrent pregnancy loss is 1%.<ref name="rcog2003">{{cite web |author=Royal College of Obstetricians and Gynaecologists |author-link=Royal College of Obstetricians and Gynaecologists |date=May 2003 |title=The investigation and treatment of couples with recurrent miscarriage |website=Green-top Guideline No. 17 |url=http://www.rcog.org.uk/womens-health/clinical-guidance/investigation-and-treatment-couples-recurrent-miscarriage-green-top- |access-date=October 20, 2010 |url-status=dead |archive-url=https://web.archive.org/web/20110104235744/http://www.rcog.org.uk/womens-health/clinical-guidance/investigation-and-treatment-couples-recurrent-miscarriage-green-top- |archive-date=January 4, 2011 |df=mdy-all }}</ref> A large majority (85%) of those who have had two miscarriages will conceive and carry normally afterward.<ref name="rcog2003"/>

The physical symptoms of a miscarriage vary according to the length of pregnancy, though most miscarriages cause pain or cramping. The size of blood clots and pregnancy tissue that are passed becomes larger with longer gestations. After 13 weeks' gestation, there is a higher risk of [[Retained placenta|placenta retention]].<ref name="ausbirth">{{cite web | date=October 2004| title=Miscarriage: Emotional considerations and support | url=http://www.birth.com.au/Info.asp?class=6620&page=13| access-date=3 January 2014 | url-status=dead| archive-url=https://web.archive.org/web/20081201112940/http://www.birth.com.au/Info.asp?class=6620&page=13| archive-date=December 1, 2008 |publisher=Birth.com.au |page=13 | df=mdy-all}}</ref>