Editing Twin (section)

====Mechanism====
Regarding spontaneous or ''natural'' monozygotic twinning, a 2007 theory related to in vitro fertilization (IVF) proposes that monozygotic twins may be formed when a [[blastocyst]] contains two inner cell masses (ICM), each of which will lead to a separate fetus, rather than by the embryo splitting while hatching from the [[zona pellucida]] (the gelatinous protective coating around the blastocyst).<ref>{{Cite news |title=Study: Time-lapse recordings reveal why IVF embryos are more likely to develop into twins |url=https://www.eurekalert.org/pub_releases/2007-07/esfh-trr070107.php |work=[[EurekAlert!]] |date=2007-07-02 |access-date=2019-08-05 |archive-date=2019-08-05 |archive-url=https://web.archive.org/web/20190805221117/https://www.eurekalert.org/pub_releases/2007-07/esfh-trr070107.php |url-status=live}}</ref>

Monozygotic twins may also be created artificially by embryo splitting. It can be used as an expansion of [[in vitro fertilization]] (IVF) to increase the number of available embryos for [[embryo transfer]].<ref>{{Cite journal|vauthors=Illmensee K, Levanduski M, Vidali A, Husami N, Goudas VT |title=Human embryo twinning with applications in reproductive medicine |journal=Fertil. Steril. |volume= 93|issue= 2|pages= 423–7|date=February 2009 |pmid=19217091 |doi=10.1016/j.fertnstert.2008.12.098 |doi-access=free}}</ref>