Editing Twin (section)

===Polar body and semi-identical twins===
A 1981 study of a deceased [[triploid syndrome|XXX]] twin fetus [[Parasitic twin|without a heart]] showed that although its fetal development suggested that it was an identical twin, as it shared a placenta with its healthy twin, tests revealed that it was probably a [[polar body]] twin. The authors were unable to predict whether a healthy fetus could result from a polar body twinning.<ref>{{cite journal
 | doi = 10.1126/science.7196086
 | last = Bieber
 | first = Frederick R.
 |author2=Walter E. Nance |author3=Cynthia C. Morton |author4=Judith A. Brown |author5=Fay O. Redwine |author6= Robert L. Jordan and T. Mohanakumar
 | date = 1981-08-14
 | title = Genetic Studies of an Acardiac Monster: Evidence of Polar Body Twinning in Man
 | journal = Science
 | volume = 213
 | issue = 4509
 | pmid = 7196086
 | pages = 775–777
 | jstor=1686613| bibcode = 1981Sci...213..775B
 }}</ref> However, a study in 2012 found that it is possible for a polar body to result in a healthy fetus.<ref>{{Cite journal |last1=Scott |first1=Richard T. |last2=Treff |first2=Nathan R. |last3=Stevens |first3=John |last4=Forman |first4=Eric J. |last5=Hong |first5=Kathleen H. |last6=Katz-Jaffe |first6=Mandy G. |last7=Schoolcraft |first7=William B. |date=June 2012 |title=Delivery of a chromosomally normal child from an oocyte with reciprocal aneuploid polar bodies |journal=Journal of Assisted Reproduction and Genetics |volume=29 |issue=6 |pages=533–537 |doi=10.1007/s10815-012-9746-6 |issn=1058-0468 |pmc=3370038 |pmid=22460080}}</ref>

In 2003, a study argued that many cases of [[triploid syndrome|triploidy]] arise from sesquizygotic (semi-identical) twinning which happens when a single egg is fertilized by two sperm and splits the three sets of chromosomes into two separate cell sets.<ref>{{cite journal
 | doi = 10.1093/humrep/deg060
 | last = Golubovsky
 | first = M.D.
 | date = February 2003
 | title = Postzygotic diploidization of triploids as a source of unusual cases of mosaicism, chimerism and twinning
 | journal = Human Reproduction
 | volume = 18
 | issue = 2
 | pages = 236–242
 | pmid = 12571155
 | doi-access = free
 }}
* {{cite journal |author=John Whitfield |date=26 March 2007 |title='Semi-identical' twins discovered |journal=Nature |doi=10.1038/news070326-1 |s2cid=85215225 |url=https://www.nature.com/news/2007/070326/full/news070326-1.html |access-date=7 February 2022 |archive-date=29 October 2021 |archive-url=https://web.archive.org/web/20211029052309/https://www.nature.com/news/2007/070326/full/news070326-1.html |url-status=live}}</ref><ref>{{cite web | url=https://edition.cnn.com/2019/02/28/health/rare-twins-semi-identical-australia-trnd/index.html | title=Semi-identical twins are rare, and doctors say they've identified the second case ever }}</ref>