Editing Superfetation (section)

==Humans==
While proposed cases of superfetation have been reported in humans, the existence of this phenomenon in humans has been deemed unlikely.<ref name=Mc2016>{{cite journal|last1=McNamara|first1=HC|last2=Kane|first2=SC|last3=Craig|first3=JM|last4=Short|first4=RV|last5=Umstad|first5=MP|title=A review of the mechanisms and evidence for typical and atypical twinning.|journal=[[American Journal of Obstetrics and Gynecology]]|date=February 2016|volume=214|issue=2|pages=172–191|doi=10.1016/j.ajog.2015.10.930|pmid=26548710}}</ref> Better explanations include differential growth between twins due to various reasons, such as [[twin-to-twin transfusion syndrome]].<ref name=Mc2016/> Artificially-induced superfetation has been demonstrated, although only up to a short period after insemination.<ref name=Mc2016/>

A 2008 French study found evidence to suggest that superfetation is a reality for humans, but that it is so rare that there have been fewer than 10 recorded cases in the world.<ref>{{cite web |title=Superfœtation: about a case and review of the literature |date=4 June 2008 |website=EM Consulte Journal of Obstetrics and Reproductive Biology |url=https://www.em-consulte.com/article/195925/alertePM |first1=O. |last1=Pape |first2=N. |last2=Winer |first3=A. |last3=Paumier |first4=H.J. |last4=Philippe |first5=B. |last5=Flatrès |first6=G. |last6=Boog}}</ref>

In 2017, it was reported that an American woman who had agreed to act as a [[Surrogacy|surrogate]] for a Chinese couple bore two babies, who were initially believed to be twins. Before the adoptive parents could return home to China, however, it was discovered that one of the babies was, in fact, the biological son of the surrogate. Doctors confirmed that the birth-mother had become pregnant with her and her partner's child, roughly three weeks after becoming pregnant with the Chinese couple's child.<ref>{{cite web|url=https://www.insideedition.com/surrogate-mom-gets-pregnant-while-carrying-another-couples-baby-37644|title=Surrogate Mom Gets Pregnant While Carrying Another Couple's Baby|date=30 October 2017|website=Inside Edition |first1=Deborah |last1=Hastings |access-date=16 December 2018}}</ref>

There have been multiple cases in the United States of women who reported twins with a difference in age of a week or less and women who reported two surges of ovulation occurring within a few days of each other. Though rare, this condition is believed to affect as many as 0.3% of women, but one twin is often lost, so the true numbers are not known.{{Citation needed|date=October 2018}}

Research has found that 10% of women release two eggs in a cycle, but both eggs are released at the end of the same "wave" of follicullogenesis, which does not support the theory of superfetation in humans.<ref>{{Cite news|url=https://www.newscientist.com/article/dn3927-women-can-ovulate-more-than-once-a-month/ |date=9 July 2003 |title=Women can ovulate more than once a month|last=Vince|first=Gaia|work=[[New Scientist]]|access-date=2018-10-22|language=en-US}}</ref>

In 2017, a woman in İzmir, Turkey, became pregnant with two babies conceived about a month apart and she gave birth to both on October 7, 2017. According to the news report this event has officially been registered in global medical records as the 12th superfetation case.<ref>{{cite news |url=https://www.hurriyetdailynews.com/turkish-woman-makes-history-as-12th-superfetation-case-172407|title=Turkish woman makes history as 12th superfetation case
|newspaper=[[Hürriyet Daily News]] |date=March 23, 2022 |url-status=live |archive-url=https://web.archive.org/web/20231116175213/https://www.hurriyetdailynews.com/turkish-woman-makes-history-as-12th-superfetation-case-172407 |archive-date= Nov 16, 2023 }}</ref> 

In September 2020, a woman in Wiltshire, England, gave birth to fraternal twins, who were conceived three weeks apart.<ref>{{Cite news |date=2021-04-07 |title=Woman gets pregnant while already pregnant, gives birth to twins conceived 3 weeks apart |url=https://www.washingtonpost.com/lifestyle/2021/04/08/conceive-baby-while-pregnant/ |work=[[The Washington Post]] |language=en-US |url-access=subscription |first1=Sydney |last1=Page |url-status=live |archive-url= https://web.archive.org/web/20231214082110/https://www.washingtonpost.com/lifestyle/2021/04/08/conceive-baby-while-pregnant/ |archive-date= Dec 14, 2023 }}</ref>