Editing Multiple birth (section)

==Human multiple births==
In humans, the average length of pregnancy (2 weeks fewer than [[gestation]]) is 38 weeks with a single fetus. This average decreases for each additional fetus: to 36 weeks for twin births, 32 weeks for triplets, and 30 weeks for quadruplets.<ref>{{Cite web |title=Multiple Pregnancy and Birth: Twins, Triplets, and High Order Multiples (booklet) |url=https://www.reproductivefacts.org/news-and-publications/patient-fact-sheets-and-booklets/documents/fact-sheets-and-info-booklets/multiple-pregnancy-and-birth-twins-triplets-and-high-order-multiples-booklet/ |access-date=2021-04-03 |website=www.reproductivefacts.org}}</ref> With the decreasing gestation time, the risks from immaturity at birth and subsequent viability increase with the size of the sibling group. Only as of the twentieth century have more than four all survived infancy.

Recent history has also seen increasing numbers of multiple births. In the United States, it has been estimated that by 2011, 36% of twin births, and 78% of triplet and higher-order births resulted from conception by [[assisted reproductive technology]].<ref>{{Cite journal |vauthors=Kulkarni AD, Jamieson DJ, Jones HW, Kissin DM, Gallo MF, Macaluso M, Adashi EY |year=2013 |title=Fertility Treatments and Multiple Births in the United States |journal=New England Journal of Medicine |volume=369 |issue=23 |pages=2218–2225 |doi=10.1056/NEJMoa1301467 |pmid=24304051 |doi-access=free}}</ref>

===Twins===
{{Main|Twin}}
Twins are by far the most common form of multiple births in humans. The U.S. [[Centers for Disease Control and Prevention]] report more than 132,000 sets of twins out of 3.9 million births of all kinds each year, about 3.4%, or 1 in 30.<ref name="Cohn-2015" />  Compared to other multiple births, twin births account for 97% of them in the US.<ref>{{Citation |last1=Gill |first1=Prabhcharan |title=Twin Births |date=2023 |work=StatPearls |url=http://www.ncbi.nlm.nih.gov/books/NBK493200/ |access-date=2023-12-10 |place=Treasure Island (FL) |publisher=StatPearls Publishing |pmid=29630252 |last2=Lende |first2=Michelle N. |last3=Van Hook |first3=James W.}}</ref> Without fertility treatments, the probability is about 1 in 60; with fertility treatments, it can be as high as 20-25%.<ref>{{Cite web |title=Twin Statistics - What is your chance of having twins? |url=http://www.keepkidshealthy.com/twins/twin_statistics.html |archive-url=https://web.archive.org/web/20080207015248/http://www.keepkidshealthy.com/twins/twin_statistics.html |archive-date=7 February 2008 |access-date=13 May 2016 |publisher=keepkidshealthy.com}}</ref>

Dizygotic (fraternal) twins can be caused by a hyperovulation gene in the mother.<ref>{{Cite web |title=Is the probability of having twins determined by genetics?: MedlinePlus Genetics |url=https://medlineplus.gov/genetics/understanding/traits/twins/ |access-date=2021-04-06 |website=medlineplus.gov |language=en}}</ref> Although the father's genes do not influence the woman's chances of having twins, he could influence his children's chances of having twins by passing on a copy of the hyperovulation gene to them.

Monozygotic (identical) twins do not run in families. The twinning is random, due to the egg splitting, so all parents have an equal chance of conceiving identical twins.<ref>{{Cite web |last=Bellefonds |first=Colleen |title=Do Twins Really Run in Families? |url=https://www.whattoexpect.com/pregnancy/twins-and-multiples/do-twins-really-run-in-families/ |access-date=10 February 2019 |website=What to Expect}}</ref>

===Triplets===
{{Redirect|Triplets||Triplet (disambiguation){{!}}Triplet}}
{{further|List of triplets}}
[[File:TripletsGirls.jpg|thumb|upright=1.2|Identical triplets like these three sisters occur when a single fertilized egg splits in two and then one of the resulting two zygotes splits again.]]
[[File:UOTW 19 - Ultrasound of the Week 1.webm|thumb|Monoamniotic triplets as seen on ultrasound<ref>{{Cite web |date=23 September 2014 |title=UOTW #19 - Ultrasound of the Week |url=https://www.ultrasoundoftheweek.com/uotw-19/ |url-status=live |archive-url=https://web.archive.org/web/20170509073218/https://www.ultrasoundoftheweek.com/uotw-19/ |archive-date=9 May 2017 |access-date=27 May 2017 |website=Ultrasound of the Week}}</ref>]]

Triplets can be either fraternal, identical, or a combination of both. The most common are strictly fraternal triplets, which come from a polyzygotic pregnancy of three eggs. Less common are triplets from a dizygotic pregnancy, where one zygote divides into two identical fetuses, and the other does not. Least common are identical triplets, three fetuses from one egg. In this case, sometimes the original zygote divides into two and then one of those two zygotes divides again but the other does not, or the original zygote divides into three.<ref>{{Cite web |title=Identical Triplets - What You Need to Know - Huggies AU |url=https://www.huggies.com.au/conception/twins-triplets-multiples/identical-triplets |access-date=2023-04-13 |website=www.huggies.com.au |language=en}}</ref>

Triplets are far less common than twins, according to the U.S. Centers for Disease Control and Prevention, accounting for only about 4,300 sets in 3.9 million births, just a little more than .1%, or 1 in 1,000.<ref name="Cohn-2015" /> According to the [[American Society for Reproductive Medicine|American Society of Reproductive Medicine]], only about 10% of these are identical triplets: about 1 in ten thousand.<ref name="Cohn-2015" /> Nevertheless, only 4 sets of identical triplets were reported in the U.S. during 2015, about one in a million.<ref name="Cohn-2015" /> According to Victor Khouzami, Chairman of Obstetrics at [[Greater Baltimore Medical Center]], "No one really knows the incidence".<ref name="Cohn-2015" />

Identical triplets or quadruplets are very rare and result when the original fertilized egg splits and then one of the resultant cells splits again (for triplets) or, even more rarely, a further split occurs (for quadruplets). The odds of having identical triplets is unclear. News articles and other non-scientific organizations give odds from one in 60,000 to one in 200 million pregnancies.<ref name="Cohn-2015">{{Cite news |last=Cohn |first=Meredith |date=October 23, 2015 |title=Rare identical triplets born to Baltimore couple |url=http://www.baltimoresun.com/health/bs-hs-identical-triplets-20151023-story.html |url-status=live |archive-url=https://web.archive.org/web/20151024022235/http://www.baltimoresun.com/health/bs-hs-identical-triplets-20151023-story.html |archive-date=October 24, 2015 |access-date=October 23, 2015 |work=[[The Baltimore Sun]]}}</ref><ref>{{Cite news |last=Keating |first=Caitlin |date=January 10, 2015 |title=1 in a Million Chance: Minnesota Mom Welcomes Identical Triplets |url=http://www.people.com/article/mother-gives-birth-to-identical-triplets |url-status=live |archive-url=https://web.archive.org/web/20150112232118/http://www.people.com/article/mother-gives-birth-to-identical-triplets |archive-date=January 12, 2015 |access-date=January 15, 2015 |work=[[People (magazine)|People]]}}</ref><ref>{{Cite news |date=August 8, 2007 |title=Rare identical triplets born in Austria |url=https://www.reuters.com/article/us-austria-triplets-idUSL0863741620070808 |url-status=live |archive-url=https://web.archive.org/web/20150904083509/http://www.reuters.com/article/2007/08/08/us-austria-triplets-idUSL0863741620070808 |archive-date=September 4, 2015 |access-date=January 15, 2015 |work=Reuters |location=Vienna}}</ref><ref>{{Cite news |last=Mohney |first=Gillian |date=December 5, 2013 |title=Identical Triplets, Conceived without Fertility Drugs, are 'One in a Million' |url=https://abcnews.go.com/Health/naturally-conceived-identical-triplets-born-sacramento/story?id=21109889 |access-date=January 15, 2015 |work=[[ABC News (United States)|ABC News]]}}</ref><ref>{{Cite web |last=Fierro |first=Pamela Prindle |date=December 15, 2014 |title=Identical Triplets |url=http://multiples.about.com/od/triplets/a/identtriplets.htm |url-status=live |archive-url=https://web.archive.org/web/20150309003513/http://multiples.about.com/od/triplets/a/identtriplets.htm |archive-date=9 March 2015 |access-date=15 January 2015 |website=[[About.com]]}}</ref><ref>{{Cite web |title=Mothers of Supertwins: Supertwins Statistics |url=http://www.mostonline.org/facts_outsideresources.htm |url-status=dead |archive-url=https://archive.today/20150118144610/http://www.mostonline.org/facts_outsideresources.htm |archive-date=January 18, 2015 |access-date=January 15, 2015}}</ref>

===Quadruplets===
Quadruplets are much rarer than twins or triplets. As of 2007, there were approximately 3,556 sets recorded worldwide. Quadruplet births are becoming increasingly common due to [[fertility treatment]]s. There are around 70 sets of all-identical quadruplets worldwide. Many sets of quadruplets contain a mixture of identical and fraternal siblings, such as three identical and one fraternal, two identical and two fraternal, or two pairs of identicals. One famous set of identical quadruplets was the [[Genain quadruplets]], all of whom developed [[schizophrenia]].<ref>{{Cite journal |last1=Mirsky |first1=A. F. |last2=Delisi |first2=L. E. |last3=Buchsbaum |first3=M. S. |last4=Quinn |first4=O. W. |last5=Schwerdt |first5=P. |last6=Siever |first6=L. J. |last7=Mann |first7=L. |last8=Weingartner |first8=H. |last9=Zec |first9=R. |last10=Sostek |first10=A. |year=1984 |title=The Genain Quadruplets: Psychological studies |journal=Psychiatry Research |volume=13 |issue=1 |pages=77–93 |doi=10.1016/0165-1781(84)90120-3 |pmid=6151205 |s2cid=43234604}}</ref>  Quadruplets are sometimes referred to as "quads" in Britain.<ref>{{Cite OED|quad}}</ref>
<!-- COMMENTING OUT CONFLICTING STATS - CHECK SOURCES Two genetically-different sets of identical twins statistically make up half of all quadruplets. Approximately 95% of quadruplets are all fraternal. -->

===Quintuplets===
{{redirect|Quintuplet|other uses|Quintuplet (disambiguation)}}
[[File:Dionnequints2.jpg|thumb|upright=1.25|The Canadian [[Dionne quintuplets|Dionne sisters]], seen in this 1947 photograph, were the first quintuplets known to survive infancy.]]
Quintuplets occur naturally in 1 in 55,000,000 births.<ref>{{Cite web |date=2006 |title=Multiples in pregnancy - twins triplets quads identical and fraternal |url=http://www.baby2see.com/multiples/multiples.html |url-status=dead |archive-url=https://web.archive.org/web/20150204054229/http://www.baby2see.com/multiples/multiples.html |archive-date=2015-02-04 |access-date=2015-04-15 |website=Baby2see.com}}</ref> The first quintuplets known to survive infancy were the identical female Canadian [[Dionne quintuplets]], born in 1934. Quintuplets are sometimes referred to as "quins" in the UK<ref>{{cite OED|quin}}</ref> and "quints" in North America.<ref>{{cite OED|quint}}</ref> A famous set of all-girl quintuplets are the Busby quints from the TV series [[OutDaughtered]].

===Sextuplets===
{{redirect|Sextuplets|the American film|Sextuplets (film)}}
Born in [[Liverpool]], [[England]], on November 18, 1983, the [[Walton sextuplets]] were the world's first all-female surviving sextuplets, and the world's fourth known set of surviving sextuplets. Another well-known set of sextuplets is the [[the Gosselins|Gosselin sextuplets]], born on May 10, 2004, in [[Hershey, Pennsylvania]].<ref>{{Cite web |date=10 May 2004 |title=The day after Mother's Day, the Gosselin sextuplets arrive |url=http://news.psu.edu/story/215904/2004/05/10/day-after-mothers-day-gosselin-sextuplets-arrive |url-status=live |archive-url=https://web.archive.org/web/20161023233314/http://news.psu.edu/story/215904/2004/05/10/day-after-mothers-day-gosselin-sextuplets-arrive |archive-date=2016-10-23 |publisher=Penn State University}}</ref> Reality television shows ''Jon & Kate Plus 8'' and later ''[[Kate Plus 8]]'' have chronicled the lives of these sextuplets. Other shows of this nature include ''[[Table for 12]]'' and ''[[Sweet Home Sextuplets]]''.

===Very high-order multiple births===
In 1997, the [[McCaughey septuplets]], born in [[Des Moines, Iowa]], became the first septuplets known to survive infancy.  The first surviving set of octuplets on record are the [[Suleman octuplets]], born in 2009 in [[Bellflower, California]].<ref>{{Cite news |date=27 January 2009 |title=US woman gives birth to octuplets |url=http://news.bbc.co.uk/2/hi/americas/7852623.stm |url-status=live |archive-url=https://web.archive.org/web/20090127213838/http://news.bbc.co.uk/2/hi/americas/7852623.stm |archive-date=27 January 2009 |work=[[BBC]]}}</ref><ref>{{Cite news |date=26 January 2009 |title=Octuplets born in Bellflower |url=http://latimesblogs.latimes.com/lanow/2009/01/a-mother-has-gi.html |url-status=live |archive-url=https://web.archive.org/web/20141220201234/http://latimesblogs.latimes.com/lanow/2009/01/a-mother-has-gi.html |archive-date=2014-12-20 |newspaper=[[LA Times]]}}</ref> In 2019, all 8 children celebrated their 10th birthday.<ref>{{Cite web |date=20 March 2019 |title=Octomum - Natalie Suleman's octuplets turn 10 |url=https://www.youtube.com/watch?v=EGynPlkvrWs |website=Sunday Night}}</ref> Multiple births of as many as 9 babies have been born alive; In May 2021, the Cissé nonuplets were born in [[Morocco]] to [[Halima Cissé]], a 25-year-old woman from [[Mali]].<ref>{{Cite news |last=Akinwotu |first=Emmanuel |date=5 May 2021 |title=Malian woman gives birth to nine babies |url=https://www.theguardian.com/world/2021/may/05/mali-woman-has-given-birth-to-nine-babies-says-health-ministry |work=The Guardian}}</ref> {{As of|May 2023}},<ref>{{Cite news |date=2023-05-04 |title=Record-breaking nonuplets celebrate their second birthday |url=https://www.africanews.com/2023/05/08/mali-record-breaking-nonuplets-celebrate-their-second-birthday// |access-date=2024-01-31 |work=africanews |language=en-GB}}</ref> two years since their births, all 9 are still living and reportedly in good health.

The [[list of multiple births]] covers notable examples.