{{Short description|Ability of a fetus to survive outside the uterus}} {{Globalize|date=February 2024|2=United States}} {{Use dmy dates|date=February 2024}} '''Fetal viability''' is the ability of a [[fetus]] to survive outside the [[uterus]].<ref>{{Cite web |title=Preterm birth |url=https://www.who.int/news-room/fact-sheets/detail/preterm-birth |access-date=24 July 2022 |website=www.who.int |language=en}}</ref> Viability depends upon factors such as [[gestational age]], [[birth weight]], [[sex]], [[genetics]], perinatal circumstances, and the availability of [[neonatal intensive care unit|advanced medical care]].<ref name=":5">{{Cite web |title=Understanding and Navigating Viability |url=https://www.acog.org/advocacy/facts-are-important/understanding-and-navigating-viability |access-date=2026-04-26 |website=[[American College of Obstetricians and Gynecologists]] (ACOG) |language=en}}</ref> There is no single gestational-age threshold that defines viability in all clinical settings.<ref name=":6" />
In modern, high-resource settings, medical viability is generally considered to be between 23 and 24 weeks' gestational age, meaning that these newborns have a <50% chance of either dying or surviving with severe impairment if active care is instituted; this applies to most fetuses at ≥24 weeks of gestation, and to some fetuses at 23 weeks' gestation with favourable risk factors.<ref>{{Cite news |date=1 December 2021 |title=Fetal viability is at the center of Mississippi abortion case. Here's why. |url=https://www.washingtonpost.com/health/2021/12/01/what-is-viability/ |access-date=24 July 2022 |newspaper=Washington Post |language=en}}</ref><ref>{{Cite news |last=Taylor |first=Derrick Bryson |date=3 May 2022 |title=Quick Facts You Should Know About Roe v. Wade |language=en-US |work=The New York Times |url=https://www.nytimes.com/2022/05/03/us/what-is-roe-v-wade.html |access-date=24 July 2022 |issn=0362-4331}}</ref><ref>British Association of Perinatal Medicine, Perinatal Management of Extreme Preterm Birth before 27 weeks of gestation | https://hubble-live-assets.s3.amazonaws.com/bapm/attachment/file/182/Extreme_Preterm_28-11-19_FINAL.pdf</ref> Globally, among extremely [[Preterm birth|preterm]] infants (<28 weeks’ gestational age) born between 2000 and 2024, approximately 61% survived to hospital discharge, with lower survival rates in [[Developing country|low-income countries]] (32%) than in [[High-income economy|high-income countries]] (69%).<ref name=":3">{{Cite journal |last1=Getaneh |first1=Temesgen |last2=Homaira |first2=Nusrat |last3=Kasaye |first3=Habtamu |last4=Tapawan |first4=Sarah Jane C. |last5=Chughtai |first5=Abrar Ahmad |last6=Lui |first6=Kei |date=2025-07-30 |title=Global inequities in the survival of extremely preterm infants: a systematic review and meta-analysis |journal=BMC Pediatrics |language=en |volume=25 |issue=1 |article-number=579 |doi=10.1186/s12887-025-05933-w |doi-access=free |issn=1471-2431 |pmc=12309206 |pmid=40739629}}</ref>
The term also has ethical and legal significance. In [[Neonatology|neonatal care]], viability may inform decisions about [[Neonatal resuscitation|resuscitation]] and intensive treatment for extremely [[Preterm birth|preterm]] newborns, particularly near the limit of viability.<ref name="pmid30171144" /> In law, it has been used as a threshold in [[Abortion law|abortion regulation]], although definitions vary across contexts and legal jurisdictions.<ref name=":5" /><ref name=":7" />
==Definitions== "Viability", as the word has been used in United States constitutional law since ''[[Roe v. Wade]]'', is the potential of the fetus to survive outside the uterus after birth, natural or induced, when supported by up-to-date medicine. Fetal viability depends largely on the fetal organ maturity, and environmental conditions.<ref>{{cite web |date=2012 |title=Fetal Viability. |url=http://www.reference.md/files/D005/mD005328.html |access-date=15 November 2012 |archive-date=5 October 2018 |archive-url=https://web.archive.org/web/20181005040816/http://www.reference.md/files/D005/mD005328.html }}</ref> According to Websters Encyclopedic Unabridged Dictionary of the English Language, viability of a fetus means having reached such a stage of development as to be capable of living, under normal conditions, outside the uterus. Viability exists as a function of biomedical and technological capacities, which are different in different parts of the world. As a consequence, there is, at the present time, no worldwide, uniform gestational age that defines viability.<ref name=":6">{{cite journal |vauthors=Breborowicz GH |title=Limits of fetal viability and its enhancement |journal=Early Pregnancy |volume=5 |issue=1 |pages=49–50 |date=January 2001 |pmid=11753511}}</ref>
The term "viability" may also refer to the assessment of an early intrauterine pregnancy as developing normally (intrauterine [[fetal pole]] with cardiac activity).<ref name=":5" /> The [[American College of Obstetricians and Gynecologists]] (ACOG) has noted that definitions of viability vary in clinical practice and has advised against the inclusion of the concept in legislation or regulation.<ref name=":5" />
According to the McGraw-Hill medical dictionary, a ''nonviable'' fetus is "an expelled or delivered fetus which, although living, cannot possibly survive to the point of sustaining life independently, even with support of the best available medical therapy".<ref>{{cite web |last1=The Free Dictionary |title=nonviable fetus |url=https://medical-dictionary.thefreedictionary.com/nonviable+fetus |website=Medical Dictionary |access-date=21 May 2019}}</ref> A legal definition states: "Nonviable means not capable of living, growing, or developing and functioning successfully. It is the antithesis of viable, which is defined as having attained such form and development of organs as to be normally capable of living outside the uterus." [Wolfe v. Isbell, 291 Ala. 327, 329 (Ala. 1973)]<ref>{{cite web |title=Non-Viable Fetus Law and Legal Definition |url=https://definitions.uslegal.com/n/non-viable-fetus/ |website=USLegal |access-date=21 May 2019}}</ref>
Various jurisdictions have different legal definitions of viability. In [[Republic of Ireland|Ireland]], under the [[Health (Regulation of Termination of Pregnancy) Act 2018]], fetal ''viability'' is defined as "the point in a pregnancy at which, in the reasonable opinion of a medical practitioner, the fetus is capable of survival outside the uterus without extraordinary life-sustaining measures" [Definitions (Part 2)(8)].<ref>{{cite web |title=Health (Regulation of Termination of Pregnancy) Act 2018 |url=https://data.oireachtas.ie/ie/oireachtas/act/2018/31/eng/enacted/a3118.pdf |publisher=Irish parliament}}</ref>
===Black's law dictionary 6th edition=== Viability. Capable of living. A term used to denote the power a newborn child possesses of continuing its independent existence. That stage of fetal development when the life of the unborn child may be continued indefinitely outside the womb by natural or artificial life-support systems. The constitutionality of this statutory definition (V.A.M.S. (Mo.),188.015) was upheld in Planned Parenthood of Central Mo. v. Danforth, 428 U.S. 52,96 S.Ct 2831, 49 L.Ed.2d 788.
For purposes of abortion regulation, viability is reached when, in the judgement of the attending physician on the particular facts of the case before him or her, there is a reasonable likelihood of the fetuses' sustained survival outside the womb, with or without artificial support. Colautti v. Franklin, 439 U.S. 379,388, 99 S.Ct. 675, 682, 58 L.Ed.2d 596. See Also Viable; Viable Child.
==Medical viability== Fetal viability is generally considered to begin at 23 or 24 weeks [[Gestational age (obstetrics)|gestational age]] in the United States.<ref name=":0">{{Cite news |vauthors=Liptak A |date=28 November 2021 |title=Fetal Viability, Long an Abortion Dividing Line, Faces a Supreme Court Test |language=en-US |work=The New York Times |url=https://www.nytimes.com/2021/11/28/us/politics/supreme-court-mississippi-abortion-law.html |access-date=8 May 2022 |issn=0362-4331}}</ref><ref name=":1">{{Cite news |vauthors=Hassan A |date=28 October 2021 |title=What to Know About the Mississippi Abortion Law Challenging Roe v. Wade |language=en-US |work=The New York Times |url=https://www.nytimes.com/article/mississippi-abortion-law.html |access-date=11 November 2021 |issn=0362-4331}}</ref>
There is no sharp limit of development, gestational age, or weight at which a human fetus automatically becomes viable.<ref name=developinghuman>{{cite book |vauthors=Moore K, Persaud T |url=https://books.google.com/books?id=dbRpAAAAMAAJ&q=%22Prematurity+is+one+of+the+most+common+causes+of+morbidity%22 |title=The Developing Human: Clinically Oriented Embryology |page=103 |publisher=Saunders |date=2003 |isbn=978-0-7216-6974-8}}</ref> According to one study, between 2013 and 2018 at [[United States]] academic medical centers, the percentage of newborns who survived long enough to leave the hospital was 30% at 22 weeks, 55% at 23 weeks, 70% at 24 weeks, and 80% of those born at 25 weeks gestational age.<ref name=":4">{{cite journal |display-authors=6 |vauthors=Bell EF, Hintz SR, Hansen NI, Bann CM, Wyckoff MH, DeMauro SB, Walsh MC, Vohr BR, Stoll BJ, Carlo WA, Van Meurs KP, Rysavy MA, Patel RM, Merhar SL, Sánchez PJ, Laptook AR, Hibbs AM, Cotten CM, D'Angio CT, Winter S, Fuller J, Das A |date=January 2022 |title=Mortality, In-Hospital Morbidity, Care Practices, and 2-Year Outcomes for Extremely Preterm Infants in the US, 2013-2018 |journal=JAMA |volume=327 |issue=3 |pages=248–263 |doi=10.1001/jama.2021.23580 |pmc=8767441 |pmid=35040888}}</ref> Between 2010 and 2014, babies in the United States had an approximately 70% survival rate when born under weight of 500 g (1.10lb), an increase from a 30.8% survival rate between 2006 and 2010.<ref name="pmid29956691">{{cite journal |vauthors=Varga P, Berecz B, Pete B, Kollár T, Magyar Z, Jeager J, Görbe ÉR, Rigó J, Joó JG, Gasparics Á |display-authors=6 |title=Trends in Mortality and Morbidity in Infants Under 500 Grams Birthweight: Observations from Our Neonatal Intensive Care Unit (NICU) |journal=Medical Science Monitor |volume=24 |issue= |pages=4474–4480 |date=June 2018 |pmid=29956691 |pmc=6055514 |doi=10.12659/MSM.907652}}</ref> A baby's chances for survival increases 3 to 4 percentage points per day between 23 and 24 weeks of gestation, and about 2 to 3 percentage points per day between 24 and 26 weeks of gestation. After 26 weeks the rate of survival increases at a much slower rate because survival is high already.<ref name="spensershope.org">{{cite web |title=What are the chances that my baby will survive?. |url=http://www.spensershope.org/chances_for_survival.htm |archive-url=https://web.archive.org/web/20180809230110/http://www.spensershope.org/chances_for_survival.htm |archive-date=9 August 2018 |access-date=14 November 2012}}</ref> Prognosis depends also on medical protocols on whether to resuscitate and aggressively treat a very [[Preterm birth|premature newborn]], or whether to provide only [[palliative care]], in view of the high risk of severe disability of very preterm babies.<ref name=pmid15032380>{{cite journal |vauthors=Verlato G, Gobber D, Drago D, Chiandetti L, Drigo P |title=Guidelines for resuscitation in the delivery room of extremely preterm infants |journal=Journal of Child Neurology |volume=19 |issue=1 |pages=31–34 |date=January 2004 |pmid=15032380 |doi=10.1177/088307380401900106011 |s2cid=20200767 |author6=Working Group of Intensive Care in the Delivery Room of Extremely Premature Newborns}}</ref>
[[File:Prenatal development table.svg|thumb|center|800px|Stages in [[prenatal development]], showing ''viability'' and point of 50% chance of survival (''limit of viability'') at bottom. Weeks and months numbered by gestation.]]According to a [[Stanford University]] study on babies born in the most advanced US hospitals between 2013 and 2018, at 23 weeks, 55% of infants survive a [[preterm birth]] long enough to be discharged from the hospital, usually months later.<ref name=":4" /> Most of these infants experienced some form of significant [[neurodevelopmental impairment]], such as [[cerebral palsy]].<ref name=":4" /> Most were re-hospitalized for respiratory illnesses or other medical problems during the first two years of life.<ref name=":4" /> Some used [[adaptive equipment]] such as walkers or feeding tubes, but most could feed themselves when they were 2 years old.<ref name=":4" /> Most had typical vision and hearing.<ref name=":4" />
{| class="wikitable" |- ! Completed weeks of gestation at birth || 21 and less || 22 || 23 || 24 || 25 || 26 || 27 |28|| 30 || 34 |- ! Chance of long-term survival with advanced medical care || <1%<ref>{{Cite web |title=World's most premature baby defies sub-1% survival odds to break record |url=https://guinnessworldrecords.com/news/2021/11/worlds-most-premature-baby-defies-sub-1-survival-odds-to-break-record-681851 |access-date=15 March 2022 |website=[[Guinness World Records]] |date=10 November 2021}}</ref>|| 30%<ref name=":4" /> || 55%<ref name=":4" /> || 70%<ref name=":4" /> || 80%<ref name=":4" /> || 88%<ref name=":4" /> || 90%<ref name=":4" /> |95%<ref name=":4" />|| >95% || >98% |}
Global estimates suggest that among extremely preterm infants (<28 weeks’ gestational age) born between 2000 and 2024, approximately 61% survived to hospital discharge.<ref name=":3" /> Among survivors, 52% were discharged without major morbidity, defined as the absence of [[bronchopulmonary dysplasia]], severe [[intraventricular hemorrhage]] (grade 3 or 4), [[necrotizing enterocolitis]] (stage II or III), or [[retinopathy of prematurity]] (stage 3, 4, or 5).<ref name=":3" /> Survival rates were lower in [[Developing country|low-income countries]] (32%) than in [[High-income economy|high-income countries]] (69%).<ref name=":3" />
==Period of viability== Beliefs about viability vary by country. Medical decisions regarding the resuscitation of extremely preterm infants (EPI) deemed to be in the "grey zone" usually take into account weight and gestational age, as well as parental views.<ref name=pmid30171144>{{cite journal |vauthors=Wilkinson D, Verhagen E, Johansson S |title=Thresholds for Resuscitation of Extremely Preterm Infants in the UK, Sweden, and Netherlands |journal=Pediatrics |volume=142 |issue=Suppl 1 |pages=S574–S584 |date=September 2018 |pmid=30171144 |pmc=6379058 |doi=10.1542/peds.2018-0478I}}</ref><ref name=AIHW-2012>{{cite web |vauthors=Li Z, Zeki R, Hilder L, Sullivan, EA |title=Australia's Mothers and Babies 2010 |url=http://www.aihw.gov.au/WorkArea/DownloadAsset.aspx?id=60129542372 |work=Perinatal statistics series no. 27. Cat. no. PER 57 |publisher=Australian Institute of Health and Welfare National Perinatal Statistics Unit, Australian Government |access-date=4 July 2013 |year=2012}}</ref><ref name=Mohangoo-2013>{{cite journal |vauthors=Mohangoo AD, Blondel B, Gissler M, Velebil P, Macfarlane A, Zeitlin J |title=International comparisons of fetal and neonatal mortality rates in high-income countries: should exclusion thresholds be based on birth weight or gestational age? |journal=PLOS ONE |volume=8 |issue=5 |article-number=e64869 |year=2013 |pmid=23700489 |pmc=3658983 |doi=10.1371/journal.pone.0064869 |veditors=Wright L |doi-access=free |bibcode=2013PLoSO...864869M}}</ref><ref name=RCOG-late-abortion>{{cite web |author1=Royal College of Obstetricians |author2=Gynaecologists UK |title=Further Issues Relating to Late Abortion, Fetal Viability and Registration of Births and Deaths |url=http://www.rcog.org.uk/womens-health/clinical-guidance/further-issues-relating-late-abortion-fetal-viability-and-registrati |publisher=Royal College of Obstetricians and Gynaecologists UK |access-date=4 July 2013 |date=April 2001 |archive-url=https://web.archive.org/web/20131105042348/http://www.rcog.org.uk/womens-health/clinical-guidance/further-issues-relating-late-abortion-fetal-viability-and-registrati |archive-date=5 November 2013}}</ref> One 2018 study showed that there was a significant difference between countries in what was considered to be the "grey zone": the "grey zone" was considered to be 22 to 23 weeks in Sweden, 23 to 24 weeks in the UK, and 24 to 26 weeks in the Netherlands.<ref name=pmid30171144/> Whether the fetus is in the period of viability may have legal ramifications as far as the fetus' rights of protection are concerned.<ref>{{cite web |title=Attorney Catherine Christophillis Discusses The Reasoning Behind The Drug Testing Of Pregnant Women |date=25 October 2000 |work=Legal News Chat Transcript |url=http://news.findlaw.com/transcripts/s/christophillis20001025.html}}</ref> Traditionally, the period of viability referred to the period after the twenty-eighth week.<ref>{{cite book |vauthors=Finney PA |url=https://archive.org/details/MoralProblemsInHospitalPractice |title=Moral Problems in Hospital Practice: a Practical Handbook. |date=1922 |publisher=Herder Bk. Co |location=St. Louis |page=[https://archive.org/details/MoralProblemsInHospitalPractice/page/n42 24] |oclc=14054441}}</ref>
Indian Law considers the period of viability to be the period after 24 weeks of gestational age.<ref>{{cite journal |vauthors=Wagh G |title=Age of Viability: Clarifying Prenatal Documentation and Definitions in India's Contemporary Medical Landscape |journal=J Obstet Gynaecol India |volume=74 |issue=6 |pages=484–8 |date=December 2024 |doi=10.1007/s13224-024-02096-z |pmid=39758573 |pmc=11693630}}</ref>
===United States Supreme Court=== The [[United States Supreme Court]] stated in ''[[Roe v. Wade]]'' (1973) that viability, defined as the "interim point at which the fetus becomes ... potentially able to live outside the mother's womb, albeit with artificial aid",<ref name="ref_59">[[s:Roe v. Wade/Opinion of the Court#ref 59|Roe v. Wade, 410 U.S. 113, 160, 93 S.Ct. 705, 730 (1973).]]</ref> "is usually placed at about seven months (28 weeks) but may occur earlier, even at 24 weeks."<ref name="ref_59"/> The 28-week definition became part of the "trimester framework" marking the point at which the "compelling state interest" (under the doctrine of [[strict scrutiny]]) in preserving potential life became possibly controlling, permitting states to freely regulate and even ban [[abortion]] after the 28th week.<ref name="ref_59"/> The subsequent ''[[Planned Parenthood v. Casey]]'' (1992) modified the "trimester framework", permitting the states to regulate abortion in ways not posing an "[[undue burden]]" on the right of the mother to an abortion at any point before viability; on account of technological developments between 1973 and 1992, viability itself was legally dissociated from the hard line of 28 weeks, leaving the point at which "undue burdens" were permissible variable depending on the technology of the time and the judgement of the state legislatures.
===Born-Alive Infants Protection Act of 2002=== In 2002, the U.S. government enacted the [[Born-Alive Infants Protection Act]]. Whereas a fetus may be ''viable'' or not ''viable'' in utero, this law provides a legal definition for personal human life when not in utero. It defines "born alive" as "the complete expulsion or extraction from his or her mother of that member, at any stage of development, who after such expulsion or extraction breathes or has a beating heart, pulsation of the umbilical cord, or definite movement of voluntary muscles"<ref>{{cite web |url=http://frwebgate.access.gpo.gov/cgi-bin/getdoc.cgi?dbname=107_cong_reports&docid=f:hr186.107 |title=House Report 107-186 - Born-Alive Infants Protection Act of 2001 |website=frwebgate.access.gpo.gov |access-date=3 April 2018}}</ref> and specifies that any of these is the action of a living human person. While the implications of this law for defining viability in medicine may not be fully explored,<ref name=Sayeed>{{cite journal |vauthors=Sayeed SA |title=Baby doe redux? The Department of Health and Human Services and the Born-Alive Infants Protection Act of 2002: a cautionary note on normative neonatal practice |journal=Pediatrics |volume=116 |issue=4 |pages=e576–85 |date=October 2005 |pmid=16199687 |doi=10.1542/peds.2005-1590 |doi-access=free}}</ref> in practice doctors and nurses are advised not to resuscitate such persons with gestational age of 22 weeks or less, under 400 g weight, with [[anencephaly]], or with a confirmed diagnosis of [[trisomy]] [[Patau syndrome|13]] or [[Edwards syndrome|18]].<ref name=Dilemma_Verge>{{cite journal |vauthors=Powell T |title=Decisions and Dilemmas Related to Resuscitation of Infants Born on the Verge of Viability |journal=Newborn and Infant Nursing Reviews |date=2012 |volume=12 |issue=1 |pages=27–32 |url=http://www.medscape.com/viewarticle/760750_6 |access-date=8 October 2015 |doi=10.1053/j.nainr.2011.12.004|url-access=subscription }}</ref><ref name=AHA_Resuscitate>{{cite journal |vauthors=Kattwinkel J, Perlman JM, Aziz K, Colby C, Fairchild K, Gallagher J, Hazinski MF, Halamek LP, Kumar P, Little G, McGowan JE, Nightengale B, Ramirez MM, Ringer S, Simon WM, Weiner GM, Wyckoff M, Zaichkin J |display-authors=6 |title=Neonatal resuscitation: 2010 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care |journal=Pediatrics |volume=126 |issue=5 |pages=e1400–13 |date=November 2010 |pmid=20956432 |doi=10.1542/peds.2010-2972E |doi-access=free}}</ref>
===U.S. state laws=== Forty-three states have laws banning post-viability abortions unless pregnancy threatens the life or health of the woman or there is a [[fetal abnormality]]. Some allow doctors to decide for themselves if the fetus is viable. Some require doctors to perform tests to prove a fetus is pre-viable and require multiple doctors to certify the findings. The procedure [[intact dilation and extraction]] (IDX) became a focal point in the abortion debate,<ref>{{cite journal |vauthors=Finer LB, Henshaw SK |title=Abortion incidence and services in the United States in 2000 |journal=Perspectives on Sexual and Reproductive Health |volume=35 |issue=1 |pages=6–15 |date=January 2003 |pmid=12602752 |doi=10.1111/j.1931-2393.2003.tb00079.x }}</ref> based on the belief that it is used mainly post-viability.<ref>{{cite journal |vauthors=Foer F |date=1997 |title=Fetal Viability |journal=Slate |url=http://www.slate.com/articles/news_and_politics/the_gist/1997/05/fetal_viability.html |access-date=14 November 2012}}</ref> IDX was made illegal in most circumstances by the [[Partial-Birth Abortion Ban Act]] in 2003, which the U.S. Supreme Court upheld in the case of ''[[Gonzales v. Carhart]]''.
==Limit of viability==
The '''limit of viability''' is the [[Gestational age (obstetrics)|gestational age]] at which a [[Preterm birth|prematurely born]] [[fetus]]/[[infant]] has a 50% chance of long-term survival outside its mother's womb. With the support of [[neonatal intensive care unit]]s, the limit of viability in the developed world has declined since the 1960s.<ref name="pmid28883097">{{cite journal |vauthors=Santhakumaran S, Statnikov Y, Gray D, Battersby C, Ashby D, Modi N |date=May 2018 |title=Survival of very preterm infants admitted to neonatal care in England 2008-2014: time trends and regional variation |journal=Archives of Disease in Childhood. Fetal and Neonatal Edition |volume=103 |issue=3 |pages=F208–F215 |doi=10.1136/archdischild-2017-312748 |pmc=5916099 |pmid=28883097}}</ref><ref>{{cite news |date=11 April 2008 |title=Prem baby survival rates revealed |work=BBC News |url=https://news.bbc.co.uk/2/hi/health/7340288.stm |access-date=11 May 2008 |vauthors=Walsh F}}</ref>
As of the mid-2000s, the limit of viability is considered to be around 24 weeks, although the incidence of major disabilities remains high at this point.<ref name="pmid16396856">{{cite journal |display-authors=6 |vauthors=Kaempf JW, Tomlinson M, Arduza C, Anderson S, Campbell B, Ferguson LA, Zabari M, Stewart VT |date=January 2006 |title=Medical staff guidelines for periviability pregnancy counseling and medical treatment of extremely premature infants |journal=Pediatrics |volume=117 |issue=1 |pages=22–29 |doi=10.1542/peds.2004-2547 |pmid=16396856 |s2cid=20495326}}</ref><ref name="pmid18240080">{{cite journal |vauthors=Morgan MA, Goldenberg RL, Schulkin J |date=February 2008 |title=Obstetrician-gynecologists' practices regarding preterm birth at the limit of viability |journal=The Journal of Maternal-Fetal & Neonatal Medicine |volume=21 |issue=2 |pages=115–121 |doi=10.1080/14767050701866971 |pmid=18240080 |s2cid=27735824}}</ref> Neonatologists generally would not provide intensive care at 23 weeks, but would from 26 weeks.<ref name="pmid17955714">{{cite journal |vauthors=Vavasseur C, Foran A, Murphy JF |date=September 2007 |title=Consensus statements on the borderlands of neonatal viability: from uncertainty to grey areas |journal=Irish Medical Journal |volume=100 |issue=8 |pages=561–564 |pmid=17955714 |quote=All would provide intensive care at 26 weeks and most would not at 23 weeks. The grey area is 24 and 25 weeks gestation. This group of infants constitute 2 per 1000 births.}}</ref><ref name="pmid16396856" /><ref name=":7">''Roe v. Wade'', [http://caselaw.lp.findlaw.com/scripts/getcase.pl?navby=CASE&court=US&vol=410&page=113 410 U.S. 113] (1973) ("viability is usually placed at about seven months (28 weeks) but may occur earlier, even at 24 weeks.") Retrieved 4 March 2007.</ref>
Different jurisdictions have different policies regarding the resuscitation of extremely premature newborns, that may be based on various factors such as gestational age, weight and medical presentation of the baby, the desires of parents and medical practitioners. The high risk of severe disability of very premature babies or of mortality despite medical efforts lead to ethical debates over [[quality of life]] and [[futile medical care]], but also about the sanctity of life as viewed in various religious doctrines.<ref>{{cite web |date=2007 |title=Critical care decisions in fetal and neonatal medicine: ethical issues: a guide to the Report |url=http://nuffieldbioethics.org/wp-content/uploads/2014/07/CCD-Short-Version-FINAL.pdf |work=Nuffield Council on Bioethics |location=London, England |access-date=30 July 2019 |archive-date=4 March 2016 |archive-url=https://web.archive.org/web/20160304040916/http://nuffieldbioethics.org/wp-content/uploads/2014/07/CCD-Short-Version-FINAL.pdf }}</ref>
As of 2025, the [[world record]] for the lowest gestational age newborn to survive is held by Nash Keen, who was born at 21 weeks on 5 July 2024 in the United States. He weighed 285 grams (10 oz) and was 24cm long (9.5 in).<ref>{{Cite web |title="Nash is pure joy in a tiny package": Most premature baby born 19 weeks early turns one |url=https://www.guinnessworldrecords.com/news/2025/7/nash-is-pure-joy-in-a-tiny-package-most-premature-baby-born-19-weeks-early-turns-one |archive-url=https://web.archive.org/web/20250805174410/https://www.guinnessworldrecords.com/news/2025/7/nash-is-pure-joy-in-a-tiny-package-most-premature-baby-born-19-weeks-early-turns-one |archive-date=2025-08-05 |access-date=2025-08-27 |website=Guinness World Records |language=en}}</ref> The record was previously held by Curtis Zy-Keith Means, who was also born on 5 July, 2020, at 21 weeks and 1 day gestational age, weighing 420 grams.<ref name=":2">{{Cite web |title=Most premature baby |url=https://www.guinnessworldrecords.com/world-records/67461-most-premature-baby |access-date=23 July 2022 |website=Guinness World Records |date=5 July 2020 |language=en-gb}}</ref>
A [[preterm birth]], also known as ''premature birth'', is defined as babies born alive before 37 weeks of pregnancy are completed.<ref name="who.int">{{cite web |title=Preterm birth |url=https://www.who.int/mediacentre/factsheets/fs363/en/ |access-date=3 April 2018 |website=World Health Organization}}</ref> There are three types of preterm births: extremely preterm (less than 28 weeks), very preterm (28 to 32 weeks) and moderate to [[Late preterm infant|late preterm]] (32 to 37 weeks).<ref name="who.int" />
==Factors that influence the chance of survival== There are several factors that affect the chance of survival of the baby. Two notable factors are age and weight. The baby's [[Gestational age (obstetrics)|gestational age]] (number of completed weeks of pregnancy) at the time of birth and the baby's weight (also a measure of growth) influence whether the baby will survive. Another major factor is gender: male infants have a slightly higher risk of dying than female infants,<ref>{{cite journal |vauthors=Morse SB, Wu SS, Ma C, Ariet M, Resnick M, Roth J |date=January 2006 |title=Racial and gender differences in the viability of extremely low birth weight infants: a population-based study |journal=Pediatrics |volume=117 |issue=1 |pages=e106–e112 |doi=10.1542/peds.2005-1286 |pmid=16396844 |doi-access=free}}</ref> for which various explanations have been proposed.<ref>{{cite journal |vauthors=DiPietro JA, Voegtline KM |date=February 2017 |title=The gestational foundation of sex differences in development and vulnerability |journal=Neuroscience |volume=342 |pages=4–20 |doi=10.1016/j.neuroscience.2015.07.068 |pmc=4732938 |pmid=26232714}} Proposed mechanisms include: :# Male fetuses mature slower than female fetuses, and thus have prolonged vulnerability. [...] :# The uterus is less hospitable to male fetuses than it is to female fetuses. [...] :# Prenatal sex steroids differentially affect the intrauterine environment and developing fetal brain. [...] :# From an evolutionary biology standpoint, male and female fetuses may rely on different adaptation strategies to maximize survival early in life.</ref>
Several types of health problems also influence fetal viability. For example, breathing problems, congenital abnormalities or malformations, and the presence of other severe diseases, especially infection, threaten the survival of the neonate.{{cn|date=August 2024}}
Other factors may influence survival by altering the rate of organ maturation or by changing the supply of oxygen to the developing fetus.{{cn|date=August 2024}}
The mother's health plays a significant role in the child's viability. Diabetes in the mother, if not well controlled, slows organ maturation; infants of such mothers have a higher mortality. Severe high blood pressure before the 8th month of pregnancy may cause changes in the placenta, decreasing the delivery of nutrients and/or oxygen to the developing fetus and leading to problems before and after delivery.{{cn|date=August 2024}}
[[Prelabor rupture of membranes|Rupture of the fetal membranes]] before 24 weeks of gestation with loss of amniotic fluid markedly decreases the baby's chances of survival, even if the baby is delivered much later.<ref name="spensershope.org" />
The quality of the facility—whether the hospital offers neonatal critical care services, whether it is a Level I pediatric trauma care facility, the availability of corticosteroids and other medications at the facility, the experience and number of physicians and nurses in neonatology and obstetrics and of the providers has a limited but still significant impact on fetal viability. Facilities that have obstetrical services and emergency rooms and operating facilities, even if smaller, can be used in areas where higher services are not available to stabilize the mother and fetus or neonate until they can be transferred to an appropriate facility.<ref>{{cite press release |title=NIH Study Reveals Factors That Influence Premature Infant Survival, Disability |publisher=NIH |date=16 April 2008 |url=https://www.nih.gov/news-events/news-releases/nih-study-reveals-factors-influence-premature-infant-survival-disability |archive-url=https://web.archive.org/web/20170211235440/https://www.nih.gov/news-events/news-releases/nih-study-reveals-factors-influence-premature-infant-survival-disability |archive-date=11 February 2017 |access-date=29 February 2020}}</ref><ref>{{cite journal |vauthors=Glass HC, Costarino AT, Stayer SA, Brett CM, Cladis F, Davis PJ |date=June 2015 |title=Outcomes for extremely premature infants |journal=Anesthesia and Analgesia |volume=120 |issue=6 |pages=1337–1351 |doi=10.1213/ANE.0000000000000705 |pmc=4438860 |pmid=25988638}}</ref><ref>{{cite book |title=Preterm Birth: Causes, Consequences, and Prevention. |last3=Outcomes |collaboration=Institute of Medicine (US) Committee on Understanding Premature Birth and Assuring Healthy |date=3 April 2018 |publisher=National Academies Press (US) |veditors=Behrman RE, Butler AS |chapter=Mortality and Acute Complications in Preterm Infants |access-date=3 April 2018 |chapter-url=https://www.ncbi.nlm.nih.gov/books/NBK11385/}}</ref><ref>{{cite news |date=6 May 2015 |title=Premature Babies May Survive at 22 Weeks if Treated, Study Finds |newspaper=The New York Times |url=https://www.nytimes.com/2015/05/07/health/premature-babies-22-weeks-viability-study.html |access-date=3 April 2018 |vauthors=Belluck P}}</ref>
== See also == * [[Beginning of human personhood]] * [[Futile medical care]] * [[Office for Human Research Protections#Additional protection for pregnant women, human fetuses, and neonates]]
== References == {{reflist}}
== Further reading == {{refbegin}} * {{cite web |publisher=United States. National Commission for the Protection of Human Subjects of Biomedical and Behavioral Research |date=May 2006 |title=Fetal Viability and Death |url=https://scholarworks.iupui.edu/bitstream/handle/1805/583/OS76-127_VII.pdf?sequence=1}} {{refend}}
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