vanishing twin

{{for|the band|Vanishing Twin}}

{{multiple issues|{{more footnotes|date=May 2018}}

{{update|date=May 2017}}}}

{{Infobox medical condition (new)

| name = Vanishing twin

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| image = Fetus papyraceus.JPG

| caption = A fetus papyraceus shown with its umbilical cord next to the placenta of its dichorionic diamniotic twin

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A vanishing twin, also known as twin resorption, is a fetus in a multigestation pregnancy that dies in utero and is then partially or completely reabsorbed.{{cite journal |last1=Landy |first1=Helain Jody |last2=Weiner |first2=Stuart |last3=Corson |first3=Stephen L. |last4=Batzer |first4=Frances R. |last5=Bolognese |first5=Ronald J. |date=July 1986 |title=The 'vanishing twin': ultrasonographic assessment of fetal disappearance in the first trimester |url=https://www.ajog.org/article/0002-9378(86)90068-2/pdf |format=PDF |journal=American Journal of Obstetrics and Gynecology |volume=155 |issue=1 |pages=14–19 |doi=10.1016/0002-9378(86)90068-2 |pmid=3524235 |s2cid=35698009}}{{cite web |url=https://sogc.org/publications-resources/public-information-pamphlets.html?id=33 |title=Public Education Pamphlets |website=sogc.org |access-date=21 December 2017}} In some instances, the dead twin is compressed into a flattened, parchment-like state known as fetus papyraceus.{{cite journal |last1=Peleg |first1=Dan |last2=Ferber |first2=Asaf |last3=Orvieto |first3=Raoul |last4=Bar-Hava |first4=Itai |last5=Ben-Rafael |first5=Zion |date=October 1998 |title=Single intrauterine fetal death (fetus papyraceus) due to uterine trauma in a twin pregnancy |url=https://www.ejog.org/article/S0301-2115(98)00128-6/fulltext |journal=European Journal of Obstetrics, Gynecology, and Reproductive Biology |volume=80 |issue=2 |pages=175–176 |doi=10.1016/S0301-2115(98)00128-6 |pmid=9846663 |s2cid=21939913}}

Vanishing twins occur in up to one of every eight multifetus pregnancies and may not even be known in most cases.{{Cite book |vauthors = Boklage CE |year=1995 |contribution=Chapter 4:The frequency and survivability of natural twin conceptions |veditors = Keith LG, Papiernik E, Keith DM, Luke B |title=Multiple Pregnancy: Epidemiology, Gestation and Perinatal Outcome |edition=1st |place=New York |publisher=Taylor & Francis Group |pages=41–42, 49 |isbn=978-1-85070-666-3 |oclc=32169252 }} "High resorption rates, which cannot be explained on the basis of the expected abortion rate, suggest intense fetal competition for space, nutrition, or other factors during early gestation, with frequent loss or resorption of the other twin(s)."{{cite journal |last1=Sulak |first1=Laura Eve |last2=Dodson |first2=Melvin G. |date=December 1986 |title=The vanishing twin: pathologic confirmation of an ultrasonographic phenomenon |url=https://pubmed.ncbi.nlm.nih.gov/3537876/ |journal=Obstetrics and Gynecology |volume=68 |issue=6 |pages=811–815 |pmid=3537876 |s2cid=68768784}} Vanishing twin syndrome has been characterized as the loss of a twin before 12 weeks of gestation, or early during the first trimester where it is uncommon for twin pregnancy to have been identified.{{Cite book |last1=Khalil |first1=Asma |title=Twin and Higher-order Pregnancies |last2=Lewi |first2=Liesbeth |last3=Lopriore |first3=Enrico |publisher=Springer International Publishing |year=2021 |isbn=9783030476526 |language=English}}

According to Boklage, most twin pregnancies are ultimately born as singles, and vanished twins are a possible source of abnormal cells.{{Cite journal |last=Boklage |first=Charles E. |date=2006 |title=Embryogenesis of chimeras, twins and anterior midline asymmetries |url=https://academic.oup.com/humrep/article/21/3/579/770117 |journal=Human Reproduction |volume=21 |issue=3 |pages=579–591 |doi=10.1093/humrep/dei370 |pmid=16253966 |doi-access=free}} In one study, Boklage reported of 325 twin pregnancies, finding that only 61 ended as twins, with 125 ending as singletons; the remainder were lost. He has estimated that for every twin pair born, there are six singletons who survived a twin conception.{{Cite news |last=Wright |first=Lawrence |date=1995-07-30 |title=The Nature of Twins |url=https://www.newyorker.com/magazine/1995/08/07/double-mystery |access-date=2025-01-12 |work=The New Yorker |language=en-US |issn=0028-792X}}

In pregnancies achieved by in vitro fertilization, "it frequently happens that more than one amniotic sac can be seen in early pregnancy, whereas a few weeks later there is only one to be seen and the other has 'vanished{{'"}}.{{cite journal |last1=Jauniaux |first1=Eric |last2=Elkhazen |first2=Nabih |last3=Leroy |first3=Fernand |last4=Wilkin |first4=Paul |last5=Rodesch |first5=Frederic |last6=Justin |first6=Jean |date=October 1988 |title=Clinical and morphologic aspects of the vanishing twin phenomenon |journal=Obstetrics and Gynecology |volume=72 |issue=4 |pages=577–581 |pmid=3047607 |s2cid=42246785}}